Rich Hanover specializes in the C&S chips. Here's a link to one of his webpages:
http://oldpokerchips.com/USPCscans.htm

You will note that a number of those chips have holes at the 3 & 9 o'clock positions. They come from USPS salesman's sample books. They were sewn onto pages, using the drilled holes to sew thread through the chip and onto the page.