I have an M1 carbine and recently came acc. a list of mfgrs. markings, so I took her down to see whats there. Rec. bolt and slide are Saginaw, the rest are a bit of this and that. I can't find any identifiable markings on the trigger housing. I'm sure its an M2 type as it has the slot for what they call a 9 spring. The only thing I found is a sort'a box on the right rear between the recoil plate lug and trigger guard. This is a definate stamping. It looks like a house on its side, flat bottom, flat sides and a sort'a off center slanted roof?? I think something is inside but I can't begin to make it out. Can anyone shed some light on this? I don't have a camera good enough to show it.