I'm not a dice expert but those would appear to be pretty old. They are not listed in the dice guide - at least not in the outdated version I have. The only ones I've seen made from that material - common name "French Ivory" - are generally from the older illegal operation like the SS Rex and the SS Tango. I have a couple of pairs but no id on them - just a number. They would most likely be from a very early time - and what the hecks up with the chicken?