Well, it is in my 1993 edition of "Cartridges of the World", where it is noted that it was concived by Ross Seyfried. Apparently, Ross had a argurment with a elephant and he found his 450 NE inadequate! No shoots were fired but Ross felt he needed something with more oomph!

Which gunmaker helped develop the cartridge is not stated however Asquare did market both the cartridge and rifles chambered for it! There are no specs in "Cartridges" but ballistics noted are:
Bullet Powder MV ME
750sp IMR4350/135 2040 6930 fpe
" " 140 2170 7845 "
" " 140 2195 8035 "
" " 160 2490 10,305 "
" RL-15/130 2235 8320 "
" " 2525 10,625 "
650sp IMR4350/160 2400 8330 "
650lead H4198/73 1660 3980 "

All loads per Ross Seyfried and used at your own risk.