Seems like I'm the only one who cares about this at the moment , but I can report an update on posts 25 and 26. Indeed some variants of the first version of the SM9 (white keys, teal accents) were made with a lefthand carriage release -- I just got a 1966 SM9 with a wide carriage that has the additional carriage release.  I bought it from the original owner, no case, and a little rust on the lower frame, but overall in nice cosmetic shape. I paid $25, which is more than I wanted to, but an SM9 is a joy forever. The segment needed treating with naphtha to cure some sticky keys, and the backspace key, interestingly, will backspace two spaces if you push it too smartly. Also, the ribbon reverse probably needs some solvent to get it working. But it generally works well. A slight disappointment is that the typeface is the Olympia no. 67 "modern" pica, which is a little bland (and the same as on my two other SM9s).

I was kidding, actually -- I just had noticed that I had posted the last three entries (before your response, of course).