I stand correct, definitely tritium sights there. You got good eyes there Mr C! I blame old age & poor eyesight
You know, it wouldn't surprise me if the official data isn't correct in places, but that's a huge change from O block all the way to Z. I never had the pleasure to talk with withergyld, but he seemed like a meticulous guy. Yugos definitely aren't my strongpoint.
ridin, refurb mark is thought to be a "TRZ" on the right side (opposite side as the S/N) on the stock:
Yugo mausers have a 1.TRZ on their stocks indicating the refurb facility.