when etching an uncoated metal, a compound is brushed on or otherwise applied to the metal. The laser engraver burns or causes the compound to darken and adhere to the metal, but it's not very durable in my experience. This is with a pretty fancy / expensive Epilog Laser engraver. The buttcaps, or really any part of the cue that wasn't metal, would be engravable. You could also charge $5 or so a pop to do easy stuff like put people's names on the Q-claw cue holders... works like a champ. If you set the speed low and the power high, it will burn cleanly down 1/16" easily. If you were ambitious, you could do cases with fancy designs or custom artwork- most programs can use images directly from the internet. Make cheap, decent looking trophies for your local league by etching the glass in a cheap picture frame ($1 for a 5x7 at Walmart)... if you solicit the bars you might be able to sell them mugs and glasses with their bar name engraved in the side. You might not immediately make your money back, but long-term you could do quite a few side jobs beyond the cue engraving you had in mind. Good luck!