Ok... No looking it up in the old catalogues, just use your best guess.  I will tell you the answer this weekend, December 10th.

8 1/2" long (straight measure, end to front tip) - 1/2" thick in the back down to a 1/16" to the tip.

I picked it with a lot of other tools off an old farm.  For a week I and a few other tool buddies couldn't figure out what it was.  I scoured the internet and Ebay but couldn't find a picture of it, absolutely nothing. I finally found it listed in one of online Plomb catalogues.  My hats off to the people who scan and post those items..

I will guess it is a seal pick.

The ends don't look flat enough for a brake adjustment tool so I'll agree with Pawpa any a seal or O ring pick.

Cotter pin puller

I updated measurements...  Great guesses so far.

8 1/2" long (straight measure front tip to back) - 1/2" thick in the back down to a 1/16" to the tip.

Used like a drift punch>? For aligning holes?

Well they made a bunch of plumbers tools for caulking  dwv pipe, so my guess is caulking iron, so I googled it and found this pic. close?

to scratch an itch if your hands are dirty !

Hoof cleaning tool ? Horse ??

Cotter pin pick?

I'd lean toward the plumbing caulking tool, too.  Seems too blunt for a cotter pin or seal puller.

Is there a prize?

I'd like to say but I'll let you guys stew on it for a while and see what happens.

Wow great guesses! My first guess when I glanced it was a punch, easy guess, because it was in a box full of chisels, punches, and other items... Then the reality of physics took over and I got a Zonk on that guess.  I never thought of the cotter pin puller, I like that one... It does make a good back scratcher.

If you don't want to wait until this weekend you can always look it up on a Plomb catalogue 1939 and most of the 1940's. Just don't say what it is.. 

Thanks..

#1) cotter pin remover
#2) hole alignment tool

I have some of those. The guy I bought them from told me they were brick jointers.