Off Topic - Bar Coding Directly Onto Metal

We have a customer that would like us to put a bar code
directly (not via a label) on a zinc plated part. Each part
does not need a unique bar code #, all they need is a
scannable id that proves that the part was actually
installed on the product. Apparently their assemblers are
forgetting to put this part on the product and they would
like to have the product pass a scanner that verifies the
installation of the part.

Anyone out there doing this?
Any ideas(other than telling them to fire their
Any Resources?

Thanks for your input!!

Marty Kuphall
Ultra Tool & Mfg.

fax: 262-703-0468