I'm sorry I never posted the results from the metal testing! Our lasers could not pierce the 0.006" aluminum. The lasers did remove the black anodized layer to expose the metal underneath, but even with multiple passes, the laser did not pierce the metal at all (there were a lot of sparks, but no sign of cutting through the metal).
Our machines are capable of etching anodized aluminum but we have little experience with the process; we could give it a try if you do not need a quick turn (since we're booked with regular plastic laser cutting right now). If you are interested, please email me a file of what you need cut (to my first name at pololu dot com). A DXF, CDR, AI, PDF, or JPG of a representative part would suffice for a rough quote. The file should show the outline of the piece, the etching within it, and the rough part size.
I will get back to you with lead time and pricing for a test run once I receive the file. For a rough estimate for etching larger quantities, please specify how many pieces you would like.