The Dietz lantern: the cold-blast patent wasn't Dietz's, and the rival who copied it became Adlake

By Matthew Partsch · Owl and Twig Vintage · September 30, 2026

Every Dietz lantern still advertises the “cold blast” design that made the name famous. The patent behind it belonged to a Philadelphia machinist named John H. Irwin, not to Robert Dietz, and the company that eventually became Dietz's biggest rival in the railroad trade got sued for copying it first.

What a Dietz lantern actually is

“Dietz” is a lantern brand, not a single object, and the shape most people picture — a tin-and-brass body, a wire bail handle, a removable glass globe over a wick burner — covers well over a century of models sold for at least three different jobs: railroad signaling, farm and barn use, and later, automotive and highway warning equipment. The company traces itself to 1840, when 22-year-old Robert Edwin Dietz bought a small lamp-and-oil business at the corner of Fulton and Columbia Streets in Brooklyn, New York, and began making candle lanterns. By the 1890s his company was the leading lantern manufacturer in the United States.

The lanterns this guide is mainly concerned with are the tubular hot-blast and cold-blast kerosene lanterns Dietz built from the 1870s through the mid-20th century — the ones that show up at estate sales with a railroad's initials cast into the globe, or with none at all. It is a different fuel and a different trademark fight from the one behind the Aladdin mantle lamp, but the same lesson applies: the name on a kerosene light rarely tells the whole ownership story. The mechanism inside a Dietz lantern, and who actually invented it, is where this one gets complicated.

Who patented the cold blast lantern

A tubular lantern has to keep a flame lit while it is carried, swung, or left outside in wind. The engineering problem is airflow, and it was solved twice, six years apart, by the same inventor — not by anyone named Dietz.

John H. Irwin, working out of Chicago, received US Patent 73,012 on January 7, 1868, titled “Improvement in Lanterns and Street-Lamps.” His method used “one or more tubes or their equivalent, arranged with one end over the burner or flame, and the other at or below the flame,” so that heat from the flame itself drove a current of air back around it. This is the hot blast principle: the air that reaches the flame has already been warmed by the lantern's own combustion. Irwin refined it on May 4, 1869 with US Patent 89,770, adding a second, symmetrical pair of tubes so that wind striking the lantern from either side would be counteracted equally, rather than blowing the flame out.

Then, on June 9, 1874, Irwin patented something different: US Patent 151,703, “Improvement in Lamps.” This version draws fresh air from a point positioned nearly as high as the chimney's own outlet — air that has not been heated by contact with the chimney at all. That is the cold blast principle, and it is the one still named on Dietz's current catalog: the company's own #80 Blizzard, sold new today, is marketed as a “cold blast” lantern, a hundred and fifty years after Irwin's patent and long after Robert Dietz himself was gone.

None of Irwin's three lantern patents list an assignee at the time they were granted. He held them himself.

The lawsuit that named a rival

In October 1874, Irwin sued a Chicago metalworking firm called Dane, Westlake & Covert for infringing his lantern patents. The case, Irwin et al. v. Dane et al., was decided in the Circuit Court for the Northern District of Illinois. The court found that Irwin was the original inventor of the patents at issue and that the defendants' lanterns infringed the combination his first three patents covered — the bell, tube, globe, and perforated-plate arrangement described above. Judge Blodgett granted an injunction against the defendants on October 29, 1875.

The firm name matters. William Westlake, a Cornish-born metalworker whose own company had been destroyed in the Great Chicago Fire of 1871, joined what became the Adams & Westlake Company around 1872 to 1874 — the same years this lawsuit was working through the courts, against a firm carrying his name. Adams & Westlake went on to become Adlake, the maker whose railroad lanterns and switch lamps competed directly against Dietz's for the next hundred years. The precise sequence of Westlake's own departure from the sued firm and his move into what became Adlake is not spelled out in the sources this guide located, but the coincidence of the name is exact: the two accounts describe the same three-partner firm.

Irwin, meanwhile, kept inventing and kept the patents in his own name for years afterward. The earliest confirmed patent this guide found assigned directly to the R. Dietz Company is US 368,950, granted August 30, 1887 (filed March 11, 1882) — for an oil-burning stove, not a lantern, but it shows that by the early 1880s Irwin's inventive output, whatever the product, was going to Dietz. By 1879, when Irwin's original 1869 lantern patent was reissued as US RE8,598, the assignees of record were two private individuals, Charles E. Sawyer and Joseph S. Dennis — not Dietz either. The company that built its reputation on Irwin's mechanism did not hold his key lantern patents at the moment they were fought over in court.

How to date a Dietz lantern

Three markings do most of the work.

• The embossed patent date on the burner or frame. Dietz lanterns commonly carry one or more patent dates cast into the metal. Collectors check an embossed date against a perpetual calendar: for most of the 19th and 20th centuries, U.S. patents were issued on Tuesdays, so a patent date that falls on any other day of the week is a sign the casting is a later copy rather than an original period part.
• Factory date codes. Between roughly 1915 and 1956, Dietz production is generally described as carrying an “M” code for the New York City factory or an “S” code for the Syracuse plant. Treat this as a guideline rather than a rule — see the records-disagree section below for a museum-documented lantern that does not follow it.
• Globe shape and base style. Fixed, non-removable globes were largely a mid-1800s feature. Tall, removable globes (roughly 5⅜ to 6 inches, often with a bell-shaped extended base) were standard from the late 1860s into the early 1900s. Short globes, around 3¼ to 4 inches, appeared in the early 1920s and remained the dominant style into the late 1960s. A tall-globe body paired with hardware from the short-globe era is a married lantern, not a factory-original one.

Country-of-manufacture markings narrow things further: “Made in U.S.A.” or a New York/Syracuse address places a lantern before Dietz's move to Hong Kong; a Hong Kong or China marking places it after 1956 and 1988, respectively.

How to tell a real one from a reproduction

Dietz lanterns have been in continuous production, under one ownership structure or another, for over 180 years, which means “reproduction” here can mean either a modern lantern openly sold as new, or an aged-to-look-old fake sold as a 19th or early 20th century antique. The tells for the second kind, according to a specialist lantern dealer's own published guide to fakes and forgeries, include:

• Chemically aged brass. A patina applied to fake a century of handling looks different under close inspection than patina that actually took a century to form — the same caution that applies to most brass-identification work.
• Thin, poor-quality casting prone to stress cracks, where an original is noticeably heavier and cleaner in its joins.
• Globe colors that were never issued. One documented Pennsylvania Railroad fake used pale blue and pale green globes — shades the dealer's guide states flatly “were never done 100 years ago” on real PRR equipment. A globe color that does not match a railroad's documented signal palette is a stronger tell than the glass itself.
• Vent holes and hardware that are poorly aligned or use incorrect components for the model.
• A magnet test on anything sold as solid brass. If a magnet sticks, the piece is plated steel, not solid brass.

None of this requires assuming bad faith on a seller's part — a great deal of what circulates as a Dietz lantern is plainly new, not aged to look old. The current Dietz brand, based in Hong Kong and manufactured in China, still sells the #80 Blizzard and several other historic model names as new production, priced new at roughly $30 to $105 depending on model and finish as of this writing. Separately, at least one American reproduction maker, W.T. Kirkman Lanterns, sells items marketed inconsistently as “Dietz style” on some listings and carrying the Dietz model name directly (a “W.T. Kirkman Exclusive/Dietz Monarch” electric table lamp, for one) on others. This guide could not confirm from public sources exactly what licensing relationship, if any, exists between Kirkman and the Hong Kong-based R.E. Dietz Co., Ltd.

The look-alikes

What the globe color signaled

A railroad lantern's globe color was an instruction, not a decoration. Museum and specialist-collector sources agree on the core signal meanings: red meant stop; amber or yellow meant proceed with caution; green meant proceed, and was also the color conductors carried at night while collecting tickets; clear or white marked a flag stop; and blue warned that workers were on or under a car, which should not be moved or coupled while that lantern was in place. Two-color globes exist as well, with green-over-clear among the more common combinations.

Collectors rank blue globes as the rarest and most sought after of the standard colors, ahead of green, amber, red, and clear, though rarity by color varies by railroad and by decade — a mid-century railroad's actual color-assignment records, where they survive, are a better authority than any general ranking. Globe glass itself sometimes carries its own maker's mark, separate from the railroad's: Corning-made globes are typically marked “CNX,” with Adlake, Kopp, and Macbeth-Evans among the other glasshouses that supplied railroad globes.

Where the records disagree

What they sell for now

Values split sharply along the line this guide keeps returning to: whether a railroad's own marking is present, cast rather than etched, and genuine.

Those figures come from a single collector price-reference site's published ranges and one cited 2024 sale, not from an auction house's own sold-lot database; this guide found no independently verifiable hammer price this run. Both LiveAuctioneers and Invaluable list completed Dietz lantern auctions with the phrase “sold,” but wall the actual realized price behind a paid account on every lot checked. Treat the table above as a reported range, not a confirmed market.

Current listings bear the pattern out at the low and high ends alike. One current eBay listing prices a genuine railroad-marked “Dietz Vesta NY” lantern, cast with “New York Central” and a run of patent dates from 1907 to 1927, at $299 or best offer. A separate listing titled “Vintage Dietz No. 20 Junior Red Railroad Lantern” is, by its own description, “new in package” and unused — a current-production lantern wearing the word “vintage” in its own title, and a fair example of exactly the labeling confusion this guide is about. It sold for $25.

New production, sold as what it is, costs less than either: one retailer's current price list runs from roughly $31 for a basic Comet-style lantern up to about $104 for a lantern-cooker combination, with the company's own model simply called “Railroad” — new, not railroad-issued, and not old — priced at $94.49.

For another mid-century lighting patent that changed hands entirely by way of a Supreme Court ruling, see the guide to Stiffel's tension pole lamp. For a different object where the base, not the badge, is what actually dates it, see the Anglepoise and Luxo architect lamps — the same lesson this guide keeps returning to, applied to a different rivalry. See more Field Guides

Sourcing railroad lanterns, barn lanterns, or other lighting worth checking before you list it?

Search Dietz lantern Search railroad lantern Search Adlake lantern