Laser based lot coding, date coding and serialization systems have come down
in price significantly. I have personally had demonstrations of laser systems
that put bar codes, ID matrix or alpha/numerics directly onto solder mask, hi
sol legen ink and directly into metal foils. These machines start at around
36k and go up to as much as 80k. 

Various suppliers offer such systems, Lumonics in Oxnard CA, TLSI in Boston
MA and several others. If you need more specific information, please reply.

Jim Morrison
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