Doug,
I'll be honest, I just dont think that checkering is original to the gun. It doesnt even look like the correct "pointed up" style that Fox used on its Utica made guns and even more so.. it doesnt seem match Philly style checkering either. The diamonds on your gun are just too nice and look to have been recently cut.
Double Gun Journal, vol. 15, issue 3, Autumn 2004, pg. 89. Excellent article by David Noreen. Pg. 94 & 95 there are two pictures that give excellent reference.

Dustin