Reply to question about 20 note organ roll:

In my experience the music for the 20-key Jeager & Brommer is
interchangable with most of the popular 20 note organs on the market
including HOFBAUER (roll playing), RAFFIN, DE LEIKA, ALDERMAN, TRUMAN,
and others. Some of the spools are not interchangable, but the music
is.

I can't speak for the extra 4 holes. From time to time some arrangers
have added holes for functions used on a specific organ, but the rolls
will still play on others. For example, Alderman produces 26 note rolls
for his unique scale, but arranges the music so it will still play on
the 20er.

Hal O'Rourke