I have seen and handled 9X56 M/S. I have considered two carbines in this caliber. From what I have read, it is just below the 9X57 Mauser in power. The Mauser cartridge is loaded to more pressure and about 100 feet per second velocity with the 246 grain bullet.
There seems little difference in the ballistics of the 9x56 and the 9.5x56 M/S. The 9.5 being loaded more often with the 270 grain bullet. The 9MM seems more common just from what I have seen.
Either would make an excellent hunting arm for medium size game animals.
We have specialty brass makers and specialty cartridge loading companies in the USA that produce both calibers.