I put them in two categories:

1. Those where something goes wrong in the design process, is corrected, and yet some chips with the wrong design get out. This would include wrong mold like the Venetian $5's and wrong number of inserts as in the Caesars $5's.

2. Those where something varies in the production process and a few chips are produced that are obviously not what was intended. These are considerably more common, and would include missing inserts as on your chip, same design on both sides of what should be a 2 sided chip, wrong inlay, etc.

There is another category that some consider errors, but which I consider just poor quality. These result from things that 'drift' in the production process, like color of ink or clay, deep or shallow hot stamp, poor registration on multi-color artwork, etc. These should be sorted out and discarded in production. I wouldn't try to collect these variations myself as there could be, in general, an unlimited number of such variations.

I don't know how to relate the kind of error to chip value. There are too few collectors of errors at this point and the guide books don't generally address the point. Number of chips with the error is much more important in determining value than kind of error, in my opinion.

DonL