No, I have no idea what they are made of. I think if you had sent an email to Art Becker he would have explained how we look at the term "Silver Strike." Are you a member of the Silver Strikers Chapter of the CC & GTCC? The ground rules of what a silver strike is was voted on at the last convention. Definition of a silver strike is defined as only those limited edition tokens produced under the rules and regulations of IGT (formerly Anchor Gaming), in conjunction with their patented Silver Strike program. This would include all denominations issued in conjunction with the silver strike program paid out of the machines or not. What it boils down to is the Riviera hologram tokens are just that "Tokens" and Art Becker's book does not cover tokens. As I said at the top Art Becker would be more than happy to discuss any issue you have with his book.
If you are interested in joining the club any number of people would be happy to send you an application and answer any questions you have.