WOW.
This is going to go down in locksport history, I don't remember a better find for a better price in all my time here.
When I was real heavy into hunting down S&G military padlocks, I pretty much had a model from each year made, from the Miracle, to the Ingersoll, to the S&G's of the early 70's, early 80's and then the 833's that came out in 1990.
There were two models that were just rarer than rare. the 844 which was a variant of the 831 but had a .844 inch wide throat, and the dual custody NAPEC. shipboard padlock. I think I saw one once on ebay but it quickly sold and for an astronomical price. antique-padlocks.com always had a photo of one and I saw some old DoD papers that had a crude drawing of one. When I was at Lockmasters during Lockcon 2012, there was one hanging at the Harry C Miller lock museum in a display case behind glass, and it was my first first time seeing that model in real life.
Yours looks pristine, and if I was still into collecting those and saw it on ebay or something, I'd easily drop $400-$500 cash for it without even thinking twice. To get it it for $25 is unheard of, so congratulations and enjoy the moment!
what a time to be alive!
Squelchtone
PS. here's some interesting reading
http://www.antique-padlocks.com/shared/ ... 381_01.pdf