This is an interesting topic (signing pieces vs putting a label on).
I had used engraving bits with mixed success (to put my business logo with e-mail, website, etc). It looks very good when done well, but due to the nature of the majority of my pieces (military unit badges that are 3D) they are very difficult to get level on the spoilboard after removing them from the waste material (I usually leave about .1" on the bottom (pretty thick onion skin....) so that the pieces don't life while cutting, so I couldn't just flip the piece over and engrave the piece while it's still flat on the front.
I have decided to go a slightly more "upscale" route (my pieces average $200-$250 CDN): engraving brass plate with my logo and then securing it to the back of the piece. I started with 3" x 6" brass plate from Michael's (craft store) but without the odd 40%-50% coupons, it's not cost effective ($25 for 4 pieces). Initially I searched out trophy blanks, etc and found eBay stores that sold different shaped brass tags (usually for stamping identifying markers for plumbing, etc), but I would have to create a jig, or some method of precisely placing the blanks so they look nice (so I could cut out more than one at a time, to keep it all time/cost effective).
I opted to go to the local Metal Superstore and buy some cutoff pieces of brass to experiment with. Unfortunately I haven't documented my attempts with the craft store brass pieces, which I used a diamond drag bit to scribe the logo, and a 1/16" Amana endmill to cut the pieces out of the brass plate (I did 6 at a time, with thick 2-sided tape to secure to spoil board... it worked very well). 24 gauge brass is a good thickness to start with (IMO) because it is rigid enough to maintain it's shape when I peeled the 2 sided tape off after they were cut out. For the new piece of brass I bought, I am going to try using a very small ball nose (1/32"r) to carve the logo, since the diamond drag experiment was OK, but not great (very faintly marked, but I'm now wondering if a second pass would perhaps improve the appearance/depth). That might have been due to the hardness of the craft store brass (no indication of type/hardness). The cutoff piece I got from Metal Supermarket was "260 half hard" and appears to be a more traditional type of brass (I was in the military and grew to hating polishing brass of all types
). For reference purposes, I paid $12Cdn per pound for the piece I bought (9" x 12") of .032 plate (I believe that is 22 gauge). Not sure what the pricing it is regularly, but for comparison to the craft store, I got 72 sq in of plate for $25CDN (excluding coupon price) and the cutoff piece (with light surface scratches that will have to be buffed off) was 108 sq in for $13CDN. If I nest things cleverly, I should be able to get quite a few tags (I'm going to make 2 or 3 different sizes of tags, to correspond to different size pieces). I'm still not 100% sure how I'm going to secure these things once I'm done, though. I was thinking of cutting a pocket on the back so that the badge will be flush with the back of the material, but I run into the "making the badge level on the bed so I can cut it dilemma", since the pocket will be fairly shallow, and any variation will be immediately obvious. I'm considering thin 2-sided tape, perhaps augmented with brass nails (more for decoration but also to secure if the tape fails). I don't like this solution, since I generally use flush mount hardware from Lee Valley, so that the pieces sit flat on the wall if/when mounted that way.
When I have the time I will post pictures (and likely create a new thread instead of highjacking the OP's thread (dig the miniatures, BTW!!! I'm not sure what .5r ball nose is the equivalent to in imperial, but I use the Amana 1/64"r bits on some of my smaller (under 6") military badges and the detail is incredible (cut times are still measured in hours, not minutes, but that's the price you pay for that kind of detail).