Is the locking block with six dots stamped on it for the Sig 220 and 220compact?

I don’t have a full size P220 to check, but the P220 Compact I have has eight indentations or “dimples” on the locking insert, four on each side.

Don’t think this helps, but my P245 locking block is stamped “45C”, my 1996 P-220 is not stamped, my 2006(stainless slide w/internal extractor) is stamped with four dots on one side, and my 2016 SAO is stamped with five dots on each side.
Will have to wait until 2026 for my next one!

Yes, SIG has used many different ways of marking (or not marking) locking inserts. Sometimes the ones that don't appear to be marked are marked on the underside.