The 20 marked on both barrels was the standard way they marked bore diameters at the first Birmingham proof. That would put them at .615" diameter at that time. Tf they were originally .626" it would have had 19 bore stamped there. Bores that are .010" over size compared to the original would put them out of proof. The .626" and .630" would mean both were out of proof which is why they had to do the reproof. Having the bore diameter marked in thousandth of an inch was standard in 1989. It looks like the barrels were cleaned up followed by a single second proof.
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Threaded Mode