Sorry for this topic drift
Actually the checking of the top strap is not defined by the -0 engineering revision.
All 5276 examples of product code 101024 have checkered top straps across all 4 of the engineering revisions
This is the top strap of my 627-1

You will notice the rounded tang on my rear sight. This indicates that the frame of this 627 is drilled and tapped for a scope mount from the factory