Curious about markings on 03A1

[Bigwagon]

I've had this rifle for about 20 years and have never done much research on it. It's SN1296108 with an SA 9-29 barrel. Can anyone tell me what the various marks on the receiver designate? It has a small O under the "6" in the serial number, a punch mark on the extractor lug area, and what appears to be a Rockwell hardness mark on the receiver rail. I seem to recall one or the other of these might have indicated a batch of RIA receivers that were transferred to SA and finished.

The rifle also has a Hatcher hole and pre-war "C" stock with no markings other than the "S" in the magazine cutoff recess and MR, which I think is a Mount Rainier Arsenal inspection mark. Other distinguishing features include a polished rear sight slide with no volley notch on the top of the leaf.

I've always wondered what the deal was with rifles like this that aren't National Match rifles but were built after SA stopped production on new service rifles in the interwar era. Appreciate any info or opinions, especially if anyone with the SRS records could check the SN.

Information

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[Tom in N.J.]

The "o" under the six in the serial number indicates that it is a Rock Island receiver, finished and numbered at Springfield Armory. I do not have SRS info.

[twh]

That looks more like a punch mark. The o referred to above is not a punch stamp but looks like a lower case letter o and sits higher on the receiver. I believe that the punch mark on the rail has a different meaning.

[fjruple]

I believe the punch marks are the inspector's approval marking for part. These punch marks were used due the hardness of the part to take a full inspector letter or code.

[XTrooper]

I believe the punch marks are the inspector's approval marking for part. These punch marks were used due the hardness of the part to take a full inspector letter or code.

This is what I've read elsewhere regarding the punch mark which is what that mark on your rifle is. The "O" referred to, when present, is normally located directly under the serial number on the curved portion of the receiver.