[Joe Camel]

sure you can lap it (but youll loose the stepping)

only thing i see a problem here is: if it were FLAT, why would only the 4 corners leave marks :shrug:

here is my 3200 Winnie after a few minutes of lapping:




and here it is after quite a few more minutes:
yep, there is copper under there.



the term is wring

** wring:
To measure with a gauge block you simply select a combination of blocks (using the fewest in combination you can, in a process called stacking) which adds up to the length you want, "wring" the blocks by rubbing the appropriate ends against each other to squeeze the air out from between them, and compare the length to the target. One interesting feature of gauge blocks is that the surfaces are so smooth and flat that once they are mated in this way they stay together unless considerable effort is used to part them. The combination of the adhesive action of the ultra-thin film of preservative oil or moisture on the blocks and the molecular attraction, or bonding, between the very flat and parallel mating surfaces, will actually hold them together.