1 Pounder (possibly 37 mm) headstamp identification


I bought this cartridge at a tag sale over ten years ago and have never been able to identify exactly what it is or where it’s from. I took it to a local expert today and he referred me to this site. Can anyone identify this? Link to images are below.


Brian - Why don’t you post the photos directly? I, and others, hesitate to open unknown links.


Here are the photos from the above link:

This cartridge is for an American “Heavy 1 Pounder” gun.

The case should measure 37mm Calibre by 137mm long with a 45mm Rim diameter.

I have seen this headstamp before (possibly discussed on the old forum). However, I can’t remember who the manufacturer was.

A 1Pdr Heavy was my first guess too. But, if the scale is correct, the case is approx 150mm long. Too long for a 1 Pdr. Maybe with the cartridge being closer to the camera than the scale throws things out of whack??


You’re right there Ray. I know I have seen this headstamp on the internet somewhere before, but I have no idea where.

I’ve seen that headstamp too, but can’t recall where. I’ll ask BOCN. They know everything.

If the neck diam of the cartridge in the picture is 37.5 mm ( data taken from municion.org) the case should be approx. 146 mm long

Measuring the picture:

neck diam = 43.60 mm
case lenght = 170 mm

43.60 : 37.5 = 170 : x

X = 146.22 mm

Would guess the stylized logo is for “WM Co” or “MW Co” if that is any help.


Thanks for the input so far, and sorry about not posting the photo directly to the forum.

So far, this has been in front of three local experts and nobody has been able to identify it.

Somebody pointed out that the camera perspective makes it difficult to tell the size. Hopefully this is helpful:

The overall length of the cartridge measures about 21 1/2 cm. The shell (from the base to the bottom of the copper ring on the projectile) measures almost exactly 14.5 cm (~5 3/4 in.)

If anyone would like me to take more photos, just let me know and I’ll do so!

1.457" Sub-Caliber?


It could be a 37 x 145 R US M4 case ( listed in Tony William’s website in the WWII pt boat ammunition section) with a 37 x 137 mm bullet

Here is a previous discussion of this headstamp viewtopic.php?f=1&t=40&p=850&hilit=johnston#p850
This is the answer to your question from Rbt. Mellichamp- world’s expert on the subject of 37mms. “The headstamp is for Johnston and Sekendoft of New York. I believe that they were only agents like Stokes Kirk or ships outfitters like Bannerman. My case looks like UMC manufacture but this is a guess.” I hope that he will get interested in the forum and answer some of these questions directly.

By the way, a long time ago I suggested storing attached photos in a separate secured server so when a person closes a Photobucket or similar account, the images would not disappear. This thread illustrates my point.

This from the resident 37mm expert over on BOCN.

[i]Generally attributed to the Johnston Seckendorf Co in NY City.

Usually 37x136, but you appear to have a 37x145 subcal case marked by them, this is unusual. Any nickel plated projectile will do, they stuffed anything into them. [/i]

And this from another member…

The mystery mark. Found on souvenir make up of surplus cases afterWW1. can have inscriptions or soldered on bits. Should be 136mm long, but who knows might have been available then frmn the surplus of the factories. Maybe untrimmed


Here is a link to a .pdf of an old manual on the 1.457" Sub-Caliber guns and ammunition from 1917.

cgsc.contentdm.oclc.org/utils/ge … me/857.pdf

A 1.7 lb. smoke shell is shown and case length is indicated as being 5.689" (144.5mm). There is also a short case version for howitzers shown with a 2.891" (73.4mm) length.

There is also a short article in issue 291/292 (pg.6) of the International Cartridge Collector (predecessor of the IAA Journal) on these two rounds.

That’s a nice item you have there that is much more uncommon than other 37mm varieties of that era though it looks like the projectile might be from a 1 pdr.


Interesting stuff. Thanks for all your help with the identification!