Little is known about the Acme No. 1, except that it appears to be a 5-point headharness KTM copy, apparently with replaceable lenses and a kidney bag filter carrier. Aside from this one photo, found in a 1930's sales offer to the Argentinian army, no photos or documentation have surfaced of the mask.

We have no idea and no info on what the Acme No. 2 looks like, if it even exists.

We really don't know what the No. 3 looks like, although apparently it used batteries to power a "reproducer", which apparently functioned as an early Voice Projection Unit. Thanks to Alexandre Hubert for this document scan.

This would have been a revolutionary concept, the first Voice Projection Unit developed in the United States, and thusly the patent shown likely refers to the Acme No. 3.


Also shown is an old photo that is speculatively believed to be a No. 3. It is taken from, and is linked below.

I am VERY interested in buying one of these.

US Patent D108879, in which Thomas O’Leary of Pittsburgh secured the right to sue other companies if they made a mask too close in appearance to what would eventually be called the Acme Full-Vision facepiece.

March 22, 1938. A. E Des. 108,879

GAS MASK Filed Oct. 6, 1937 Patented Mar. 22, 1938 UNITED STATES Des. 108,879


Thomas A. OLeary, Pittsburgh, Pa., assignor to Acme Protection Equipment Company, a corporation of Pennsylvania


Application October 6, 1937, Serial No. 71,997

Term of patent 14 years


Figure 1 is a front elevation of the mask.


Fig. 2 is an elevation with the line of observation at right angles to one of the lens.

I claim: The ornamental design for a gas mask as shown.

(signed) THOMAS A. OLEARY.

The Acme No. 4 was the first mask to bear Acme's signature "tear drop" lenses (as covered in the above design patent), and was produced in a variety of forms, differing slightly as the design advanced. This early photo shows one with crimped lenses, an oddity for Acme.  The design continued to be produced for several years afterwords, in different forms. Acme repeatedly tried to market the No. 4 and it's other face-pieces to the US military, with no success beyond some experimental trials.

While the facepiece design was patented in 1937, production of the No. 1, No. 4 and No. 5 has been documented as early as 1934. It is suspected that these early masks may have used chin welds, although it seems more likely they used an early form of injection molding, or a specialized combo of pour molding and rubber welding to manufacture integrated tissot tubes.

The No. 5 closely resembles the No. 4, but exclusively uses a chin filter. The pictured mask uses two exhale valves on the cheek, but some have been found with chin flapper valves.

Shown here is a later edition of the No. 4 facepiece. Note the flapper exhale valve, a feature unique to the No. 4 and some rare variants of the No. 5. Also note that this example, as is common for surviving No. 4 masks, uses a lens retaining band that can be released with a screwdriver, for easier replacement of the lenses, instead of a crimped lens like the previous examples.

Development of the No. 6 facepiece started sometime in the 1950's, and by 1960 the No. 4 was no longer being sold. No. 6's came in a variety of configurations, seeing multiple canister types, and being arranged for chest, chin and back filters.  

The most notable change between the No. 4 and the No. 6 was the implimentation of a peripheral exhale valve, which surrounded the mask's air intake and gave it a distinctly streamlined look. 

The No. 6, and the later No. 8, were both available in a "Speak-Ezee" configuration with an early VPU. More info can be found on Speak-Ezee's at the link below.

The Acme No. 8 facepiece was developed sometime in the 1970's, speculatively. It can be told separate from the No. 6 (Aside from the forehead stamp) by a circular boss directly centered between the lenses and the valve mechanism.  This boss was added as an easy attachment point for Speak-Ezee microphones, which required a small hole to be pierced through the mask's facepiece.

No. 8's are fairly common on the market, and can be found with both Acme and Scott/A-T-O (Scott's parent company) markings on the forehead.

Acme/Scott also manufactured a half mask, called the Duo-Seal. It uses the same valve mechanism as the standard Acme masks. Some differential colorings and purposes exist, including both cartridge respirators and small aircraft oxygen masks. (c) Moulage, 2017. Drawings (c) Canis-Infernalis.