I find nothing about a 500 Jeffery Rimmed , but the 500 Jeffery rimless is a obsolete cartridge, that is also known as the 12.7X70 Schuler. The exact origin is a little cloudy. It is a rebated rimless cartridge, with a water capacity of 160.19 grs water. Brass must be turned from solid brass rod, as the are no cases to form it from, according to THE HANDLOADER'S MANUAL of CARTRIDGE CONVERSIONS , by Donnelly.

According to COT #8, "the 500 Jeffery was a proprietary cartridge developed by Schuler in Germany, for bolt action rifles".

It was developed for Mauser bolt rifles, and Jeffery picked it up for their Mauser rifles as well, which were, more than likely, Mauser barreled actions made by Schuler. This cartridge,even if available, would not be suited well the double rifles! Ballistics, however, are similar to the 505 Gibbs!

Hope that helps!