John Tuttle asked, "How many pneumatic player pianos are there?"

Funny you should come up with that question.  I was just wondering the
same thing a few weeks ago.

I found (unfortunately I can't remember where) an article that said
there were approximately 250,000 players manufactured per year between
1920 and 1929.  Dividing that number by the 578 piano manufactures on
your list, divided by 365, works out to 1.18 pianos per day, per
manufacturer.  Seems reasonable enough.  That would be 2.5 million for
that ten year period.

Assuming that the industry started around 1900 and cutting the number
manufactured by 1/4 between 1900 and 1920, that would be an additional
1.25 million.  These are obviously real rough figures, but a plausible
ballpark.

Take Care

Tim Mattice