the 4x1-2 is a 4x1 28 throat. The 4x is I believe shallower than the 4S, the 4s is yes, the symphonic. The 4x is for the guy who can't use a 3x, or needs a larger 3x. A lot of folks get the - confused with the x. I believe the 4x have more of a C cup where the 4s has that V look. (please correct me if I'm wrong on this)
As for the rims, I did not use the term "high point", I used "contour of the inner rim/cup". This was brought to my attention by I believe it was Brad Goode. He put a dime into each 1,2 and 3 series piece and discovered the rims were all the same. It was only the inner bite that made a difference.
Back in the day, my father didn't let all the sizes into any one persons hands because he thought they would figure out his simplicity approach.
Also.... The 4s1 and 4s2 appear (by eye anyways), that the 4s1 is a flatter/cushion rim, the 4s2 is the thinner rim. I believe this is also the difference in the 4x1 and 4x2, the 4x1 being the flatter rim, the 4x2 being the thinner. But these again are not as deep as the "symphonic". I think my father was refering to the general size. Or it is possible that he changed a model# to accommidate another concept over the years.
Yes, he was super secretive. Whenver I asked him about the pieces he would just point to his head and say "it's all up here".
So folks, as much as you think I know, I am guessing too! Actually most of everything I have learned, has come from hearing from those who purchased pieces and informed me their thoughts. I would take that and what I knew already and try to make sense out of it.