I’m not familiar with this marking.
The link you provide states that:
Thanks, after looking at Alex’s site and seeing it stamped on the side I do remember seeing it before. Being on the top like this through me off.No it can't, the link you provide states that:
(information courtesy of Vic Thomas)"
This is wrong, the accuracy test marking is different. The 7.62x54r site contains a lot of wrong information and is not a good reference source.
The correct information is on Alex's site: Markings, stamped during rifles & carbines production | m9130.info
It's a "strengthened" cartridge test, do a search for that word on his page and you'll see the info
That's my thought also. Currently I don't have image with this marking on a gun (but I saw it many times), only on the PU scopeI don't think this marking is the same as the concentric "00" marking. Alex's page states that the circle inside a circle wasn't used until the early 1930s. Also, it was usually on the right side of the barrel, and it was shaped different---the circles were elongated. The marking could also be an uknown repair depot. Circle inside a circle is listed on the page as an unknown repair depot, although he doesn't provide a photo of what the marking looks like. But, your circle is in the general area where the repair depot markings were stamped. The circle in circle reference is towards the bottom of the page.
Detailed information about markings used during Mosin rifles and carbines repair and refurbishment. Section covers markings used by various repair bases, depots, stocks, Arsenals, including famous so called MO "Defence Ministry" and "1 in triangle DDR" markings.www.m9130.info