It is one of the man churned out and passed thru the proof facility in May of 1969. There should be a quality stamp on the left side of the aft lug. The 4 Rings is a Russian steel type, Izhevsk 50 A crucible steel, 4 Ring Special Gewehr Lauf Stahl SG 1, that was a replacement for the dwindling stock of Krupp/Sauer 3 Ringe Stahl. There should be a steel type stamp just forward of the flats.

A thread on the topic - http://www.doublegunshop.com/forums/ubbt...true#Post172682

Kind Regards,

Raimey
rse