The ontario knife company has been around a long time, they are the makers of the "old hickory" line of kitchen knives that have been popular for generations
http://www.ontarioknife.com/specplus_pg1.html
They were also the makers of the original USA mil-issue machete IIRC, I still have one of their 22" machetes, if youre in the bush they are about as good as it gets
The coating appears to be a typical mil-spec manganese phosphate parkerizing, that would make it newer then 1960, before then zinc phosphate was more commonly used (light gray finish, sometimes found with a green patina from long term storage with cosmoline).
(i have manganese phosphate parkerizing tanks in my basement)
Nice knife, but probably not mil-issue... you may write them and send a photo just in case... either way that doesnt mean he didnt buy it himself and use it in theater
They like using 1095 carbon steel, easy to sharpen and holds a good edge... but without the parkerizing, will rust easily.
You can use hot naval jelly to touch up the manganese phosphate parkerizing (old trick), just dont put it on any other surface type, apply and let set till the color matches (naval jelly contains phosphoric acid) . It will also safely remove the rust...but be patient, may require repeated applications. Main thing is do not sand or use anything aggressive
Brownell's also sells touch up paint
Av