Many thanks to Bob Hodge for his link to the Music Trades Review
article.  Although it tells us nothing more about Lockwoods before
1908, it does indicate that H. J. Cullum was involved with the
automatic piano trade -- if an Autotone is an automatic piano?
(I've never heard of it, and it doesn't feature in the index of
the Bowers' Encyclopedia, for example).

Also very interesting for me was the revelation that Cullum was
involved with another London agency, Blankenstein's, a connection
I hadn't made.  Blankenstein's and Lockwoods are the only two London
firms, as far as I know, who managed to obtain redundant components
from the Gramophone Company, so the connection makes sense.

Christopher Proudfoot