I have an 8x57 Guild rifle with no proofs, I have 2-9x57mm'that have been proofed in the late 20's. Is it common to see these with no proofs? I suspect it may be a post war rifle as it has a flat plastic but plate. I shoot mostly cast bullets, and have shot "full-house" jacket bullets, but am getting a bot worried that it may not be safe. It does have a serial #11 on the barrel and bolt, but the small ring receiver has been scrubbed except for the occasional number or letter mark.