There have been lots of minor running changes during the production run of 73s by Uberti. One major change was around 2008 when they changed the bolt and firing pin extension to a better design. The old ones used a small (.060) pin to hold the firing pin extension into the bolt. The new ones use a large flat plate held in by the forward carrier pin. If it's in good shape and the price is right it should be fine. However, a lot of people claim that the newer bolts are made from softer steel. Uberti says the steel is the same, but there do seem to be a lot more bottom tab failures on the newer bolts.