Geoch, that is interesting. I am not sure it is completely accurate. The 407/23 was offered in Japan for a couple of years before Allen Wright became the Australian distributor, and I see far fewer 407/23s outside of Japan than in Japan. I am almost certain it was not specially manufactured for non-Japanese markets. It is possible that the '23' came from Allen Wright, but I am not even sure of that. Perhaps it had the name 407 (without the 23) when it was first sold. I do not know and the only way to confirm that would probably be to check an old copy of Stereo Sound.
Personally, I had always assumed the 23 was for ~23cm length (the way the 506/30 has a ~30cm length). It is true that at 233mm, to get Baerwald alignment, it almost has to be 23 degrees offset angle, but that won't get you the cart straight in line with the headshell. And there is no way that the 506/30 is going to have a 30-degree offset angle...
I am not sure of your question. You can twist the cart in the headshell on all the SAEC arms (and it might make more sense to change the mounting distance too) to bring them to Baerwald. All but the 317 have original mfr geometry specs which are more aggressive than Stevenson alignment as far as I remember.
I have not had the problems Dertonarm has mentioned. I can understand the concept, but I think that the change in resonance from setting the cart off-line in the headshell is going to be substantially less of a problem than one's choice of headshell, one's cart match, and/or the resonance inherent in the arm itself.
