The other day I was rebuilding an Altette horn and wondered how many different types were fitted to the A7/A10s.
I went through my pile and the Lucas book and found there were five different Altettes, HF 1441 and 8H.
One HF 1234 was used until 1948, identified by a flat back with an adjusting screw and two point mounting screws.
In 1949 a modified HF 1234 was fitted which has an indent on the back with rivets, no adjuster and no flats on the sides where the bracket fits.
In 1950 the 1949 type was modified with flats on the sides. This one was used until 1952.
In 1953, the Plunger models had the HF 1235 which is the cheap version of the HF 1234, having screws on the bezel instead of acorn nuts and painted finish, no chrome. The body was modified with a point adjuster and pole adjuster on the back, identified by a large nut and small screw.
The Swinging Arm models had the HF 1234 which had a different appearance to all previous types.
The body was as the HF 1235 described above but the front had a chromed bezel, chromed dome bolts and a corrugated tone disc.
This was fitted to all bikes until 1957 and to bikes without a nacelle until 1963.
The nacelle models had the HF 1441 fitted until about 1960 and thereafter the much smaller [and lighter] 8H was used.
There were also colour variations which I have not included.
The HF 1234 had two different brackets, depending on the bike they were fitted to. The Plunger/Rigid had a straight bracket and the Swinging Arm had a cranked bracket for the horn to clear the generator.
Hopefully I haven't confused everyone!
Trev.