Any thoughts?  I automatically guessed Colt for the C seems to be on a raised "pad" but the other picture of a verified Colt rear sight in the upper still is different. The shape inside the "C" doesn't appear to be a 1.  Perhaps it isn't even a C.

Generally earliest original Colts had no markings,/pads/numbers until GM and H&R came into the game then Colt's were marked as on the upper receiver with rectangle pad and number inside a circle and not like aperture beside the windage drum.  That one looks like Colt except no rectangle pad.  Could be a blem for lack of better term.  Probably sub contract replacement part.  

Possibly H&R or GM that were different in some instances.  I have one that is a raised pad only with two horizontal lines through the rectangle pad only. Always though it was H&R but had it so long now couldn't tell you provenance or really care.  Know it was different than all the others I've had and always held on to it.

These were taken off a GM upper that went through some sort of rearsenal process.

The marking on the sight looks like a Y inside a O... Didnt olympic arms used this marking on their bolts?

Is that aperture "L" marked?

Yep......   Here is a picture.


Something odd I noticed last night while taking some pictures of some Canadian 30-06 AP ammo I'm selling. The "C" symbol on the sight bears a resemblance to the C symbol on the headstamp of the Canadian ammo.