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?