Hi Nicholas,  thanks for your answer!  As far as I know, it is a player
piano, but I have asked the owner to make photos of the instrument,
including the inside; and the tracker bar, if possible with
measurements.  Maybe we'll learn something from that.

(There is a chance that the number is wrong -- getting information
is not always that reliable here -- but we'll see.  If all else fails,
I might go on a trip to the Black Forest!)

Many regards,
Harald Müller
Grafing near Munich