The question was posed "What was the purpose of the knurled edge on crest and seals"

I looked over my chips and found that I had the following knurled chips (see scan). What I found interesting was that, in several cases, the club ordered round or square edge for their lower denomination or roulette chips and knurled chips for their high denomination chips.

Some examples:

1) SS Rex - square edge for the 5 & 10, knurled edge for the 50

2) Hollywood Dinner Club - square edge for the 5 & 25, knurled edge for the 100

3) Chesterfield - square edge for the 5, knurled edge for the 10, 20 & 50

4) Agua Caliente - round edge on the ND and 5, knurled edge on the 25 & 100

5) Gran Cafe - square edge on the roulettes, knurled edge on the 25

It seems to me the the knurled edge was simply an added security for the more valuable checks. Had there not been an extra charge for the knurling process, all chips (at least for the examples above) would have been knurled.