Vintage Gravity Knife Nickel Silver OTF

I've had a few of these old all metal gravity knives and there are differences between them. This one has a non magnetic frame which looks like nickel silver. There are no markings on the knife. The knife measures 7 5/8 inches open and the flat grind spear blade is very nice with the original factory finish with a few very light scratches. The knife works perfectly. The blade falls out and locks when held down and lever is pressed and falls back in nicely when tipped up and lever pressed. Not sure if these had any military, or espionage use, but I could see that being a possibility. Very nice condition.