Mike; A pit boss at Harrah's told me that they put the back up $2.50's out (HAR-2.5b) because they were running low on the HAR-2.5/2.5a chips. Prior to this release, there was only "one known" listed in my A.C. catalog .... and that was a notched specimen. So be careful now on ebay ... where dishonest sellers may list this chip as "one known" according to Black's Catalog.