Paul:

You and your "junk" boxes! :o) The 10-20-30 has to do with the grading of the chip in C&W's book. The three "ranges" of values are: GD30, VF65, and CS90 ("Chip State") They also assign a "rarity" number based on their knowledge of approx.numbers of that particular chip known to exist. R-6 is "Rare" with 31 - 75 known examples.

I hope this helps. I'm sure if James is reading this board (as he often does) he would be glad to give you more detailed answers to your questions!

Talk to you later!

Rich in Lake Forest