elbowroom

I have an old file that I would like to identify. The only mark on it is a 5 point star with the letters SF over CO inside the star. Anybody know which file maker used this logo? I have forged it into a knife and ready for heat treatment. Trying to determine what steel it is

Thanx guys. Just getting my feet wet here. Working a first set of tongs. Doesn't take long to work up a sweat with burner running full time

Has anybody put an inline propane shut off valve on a forge to shut the forge down while hammering? Seems like it would save a lot of fuel and keep the shop cooler. Would it be safe to restart a hot forge?