think I know it good enough.
its called 11,5x60R 450 and you find it from time to time http://forums.nitroexpress.com/showflat.php?Cat=0&Number=109928&an=0&page=0#Post109928

its a cut down 450 BPE but the "facon allemande", very close in power to the 11,15x60R Mauser round. reloading stuff is allready available, including brass from Horneber.this catridge have seen the good old days also in Elsaß-Lothringen before such brand new smokless rounds like 8x57 IR killed it.
if you ask me, dont trust this new smokless powder hype, it will go away.

I have a gras M73 action laying around here and look for a 500 BP barrel to make a 12,7x60R 500 single shot from it some days. the bolt head of the gras will fit the 32 ga/500 BPE size.