Looking for information on M2 25 ounce bar

Picked this up today but I have been unsuccessful with finding any info on it. Anybody know anything about M2 or this bar? Thanks!!!

 

American from the very little info on the net. Where did you buy it?

 

Silver coin section??

Wrong section

 

Yes, I would say "us" bar!

 

Yea no info that I can find. I only found one other M2 bar and it was on a blog post from 2013, I contacted the individual regarding it, but he said he had no information on M2. I purchased from a large LCS in my area.

 

Read somewhere, circa 1970.
Can't find the link now.

 

Got a list of "M" mark silver bar and "M2" was there.

M & B Mining, Inc.
M2
MacKay, B. R. & Sons, Inc
Magnum Drew Company
Manfra, Tordella & Brooks
Mark Refining
Market Harmony Bullion
Marshal, E.D., Refiners
Martin Metals, Inc.
Mastiff Metals
Materion Mining Company
MC
MCR
MDC
MDM
.
.
.
etc

Found 5 oz, 20 oz and your 25 oz.

 

Do you guys think this was a small little mint at one time? Thanks so far for the research!