I read up a bit on these and know that I should NOT shoot full power .308 or even 7.62x51 in this thing. I reload and will downgrade my loads for this. Actually I have a ton of these blue plastic training rounds I will probably shoot a lot in this.

But what is odd, at least to me, is there are no markings on this thing at all. Except for the import markings under the barrel from samco, and a serial number on the receiver, and a couple number marks on the mag plate and bolt, there is nothing.
Is this odd?

no if you look these up in the value books there are 2 proces one for marked one for unmarked. that is for 7mm not the 308 conversions.