"No" on the codes, they were just put on the receiver ring. Usually the Yugo K98s will still have WaAs on the trigger and sear, the ejector box, and sometimes the rear sight leaf/ upper part of the base. They were fairly thorough. *IF* all remaining Waffen proofs are the same, chances are they are original to the rifle, and you can track it pretty close by that. All numbers match because what didn't was neatly ground and restamped, unlike the Russian electro-pencil overstamps. Lineouts were common with the Yugo captures.
No reason not to like 'em, so long as you can live with a German rifle with a Yugo crest and prezudece 44 on the receiver and 1TRZ in the stock.