Went to a small town gun show and a guy I know casually who works in an LGS in another town had this beautiful custom rifle on a commercial Mauser action chambered in this. I'd never heard of it before, but I'm pretty sure from what I've found, this rifle is one of Gradle's and not one someone else made.
The round pre-date the various 7mm magnums (late '40s, early '50s) and is made by modifyuing a .348 Winchester case. The rifle came with a set of dies and 30-40 formed cases. Rifle Magazine had a pretty good article on the cartridge a few years ago, and looking at them side by side, it looks real similar to the 7mm WSM case, might even be able to use 7mm WSM brass to make ammo somehow.
Anyone else ever heard of this? Considering the work, the Zeiss scope and Stith mount, that rifle would be obscenely expensive to make today, think $3000-$4000, I would guess. The stock work and finish on this thing was breathtaking.