NavList:

David, the Marks IX A, IXBM have the same works, except that the averager is two speed and a 2 power telescope has been added to the BM, i.e. in each case you have a "fresh cast" IXA body with a choice of averager and addition of telescope. Yhe Mark IX has different works with only a six shot averager.

Bill Morris

Pukenui

New zealand

Bill.  I was issued with a MkIXBM during training in the 60s, but I had to hand it back when I progressed onto peri-sextants in 1968.  I now actually own two MkIXAs and a MkIX.  Last week, when I was in London, I was asked to look at two MkIXAs and a MkIXBM at the RIN.  The reason I asked was because the MkIXBM (last serviced in 1963) appeared to be something of a hybrid.  It had a two position averager, a double eyepiece, and a ‘wiggly pig-tail hanger’ but the left hand side casting had the original MkIXA and the relevant stores ref and section number poorly ground out and a new stores ref and section number and MkIXBM stamped alongside it.  Obviously by 1942 or 43 it was waste not want not, but I was wondering they ever cast left hand sides afresh for later MkIXBMs or if they had so many MkIXA sides unused that thy never needed to cast any new ones for the MkIXBs and BMs.  DaveP