Early Conn 6M Model : facts and rumours.
There is a lot of info (and rumours) on the internet about the early 6M alto saxophone model. As far as I can determine after years of online research and reverse engineering on my own stock of saxes, I come to the following conclusions:
1) The earliest Conn alto saxes with the full 6M valve work start around series M250xxx. Series M250385 has the 6M-style left pin plateau: series M249926 still has the old ChuBerry left pin plateau. Although they do not yet have the 6M stamp, they are considered the ´early 6M´ alto´s.
2) These early 6M models still have the swivel thumb rest and the old-style microtuner (with the double ring) like the Transitional models.
3) Around series M2535xx (mid 1932), all alto´s have the extra A added after the serial number and have the 6M wire-breech guard.
4) The ´real´ 6M model no longer has the serial number M-prefix or added A and starts around series 278000 (early 1937). It has the standard thumb rest and the improved neck with the knurled coarse microtuner, as well as the VIII stamp on body and neck.
5) The last 6M VIII model was probably built in late 1945.
6) The first 6M model without a VIII stamp was introduced in early 1946, so shortly after Conn restarted production after WWII.
7) The same conclusions apply to the 26M `Connqueror` models. As far as I can tell, no 26M was built after Conn stopped saxophone production because of WWII in early 1942.