One of our North West Player Piano Association (NWPPA) members (in
North West England) has a Cecilian 'push up' which I believe is fitted
with the 'Interchangeable tracker boards' that Julian Dyer has.

Cecilian were not a large player in the industry and found that by
limiting their owners to their own non-standard roll they were probably
missing sales.  Around 1903 (I think) they introduced the rather clever
'interchangeable tracker' which immediately allowed access to all
'standard' rolls, i.e., 65-note rolls.

There is a copy on the Internet of one of their adverts for this --
just Google on <Cecilian piano player magazineart.org> (note that
"magazineart.org" is all one word) and look at the first image of
a lady seated with the player at a grand piano.  The text starts,
"A Great Advantage - The new interchangeable tracker board..."

Of course what actually happened was everyone bought 65-note rolls,
which were available in a wider selection and were probably cheaper.
The 'Cecilian' tracker was put in its box and eventually got lost.
It is possible that some Cecilian owners now don't even realise that
their tracker can be swapped.

From Julian's description he has the 'Cecilian' tracker; now all he
needs is to find Push Up No. 4979 to fit it onto.  I can find no record
of these ever being fitted to those 'newfangled' inner players.

Bob Kissick