buckstix,
Of course, you are reasonable to use the .375 Steyr now that you have determined they are so similar. It is less likely that differences in "proof" pressure between the old and new cartridges will result in problems in a bolt rifle. Like furmann, I also found Dixon's reference to the 9.4x60 Hunting, Roth case #724 1905-1914. Given the differences between nominal and actual dimensions with some cartridges, I thought that might be the same cartridge and was trying to confirm it. That is moot now.
Mike