[chris vickery]

Another way to raise serial numbers might be to try dye penetrant.
You spray on the dye, let it dry and then spray on the developer.
It is meant for searching for cracks in metal, especially welds but I believe dye penetrant would also show up stampings as the metallurgy is different in the stamped area from the base metal; it was essentially stressed when it was stamped.
I have also heard of acid etching which "raises" the number as well. Google it and there is all kinds of info