This beefy 6-inch tool is still useable. The shaft is 5/8" OD, and the jaws are 1/8" thick.  The jaw opening is 1 3/32".

The complete legend stamped on the handle reads, on a line-by-line basis, as follows:

J-1041
TRANS. MAIN SHAFT
SNAP RING REMOVER
39 BU. OLDS. PONT. 6 - 8
H M CO. USA.

I have hung on to this tool against an eventual need for it.  None has arrived so far!  Anybody have a clue about HM Co.?

>Anybody have a clue about HM Co.?

The H is a K

Kent Moore co.

The tools is in my catalog, fits the Standard transmission, 39 Buick, 1939-1950(+?) Olds, and all the Pontiac transmissions with Syncros....

In 1950 it would have set you back a pretty $2.75

Unusually large amount of text for a KM tool, generally you are lucky if you can find a number..

Re: H vs.a K:  An easy enough mistake to have made, Rusty.

Wow...that is a horrible K....

Rusty:

We were taught in school that that letter is called "H" as in, say, in Humble Pie.