Ivory or Bone? grips

let me preface this with, i am not an expert on grips so i will try and list all i know. first as you can see in the pics they have mellowed to a nice yellow color. they are not plastic but what they are is a mystery to me. i can see a grain going through them but i cannot tell if it`s an ivory or bone grain. they appear to be very old. on the inside unfinished surfaces you can tell they were cut and not a poured substance. i have had them for more years then i care to remember and only recently found them in some old gun parts box. on the flat side there is some writing but i cannot make it out. they appear to be from a single action revolver but i don`t know if it was a percussion or metallic cartridge revolver. the dimensions are, 3&1/4" high by 2&1/4" at widest point on base, and 1/2" thick. if you look at the flat side (inside) you will see the faint writing and an area where i scratched the surface with a knife to see if the color was from age or in the material. i was satisfied the yellow color came from age. PLEASE BE SURE YOU WANT THIS SET OF GRIPS AS THERE WILL BE NO RETURN UNLESS IT TURNS OUT I AM SERIOUSLY WRONG IN MY ASSESSMENT AND THEY TURN OUT TO BE PLASTIC. NO OTHER REASONS FOR RETURN WILL BE ACCEPTED. shipping will be $10.00 UPS insured to lower 48.

[Information added 03/16/2008 6:36:11 AM]

it has been suggested that perhaps these have been carved from moose or other large antlers. i figured that possibility was worth posting.

[Information added 7/6/2010 6:24:57 ]

A FELLOW GUNBROKER-ITE HAS SUGGESTED THAT THESE GRIPS ARE FOR A SMALL FRAME COLT SUCH AS THE SA 22LR.