This is sad news.  I got to know Mac very well during the more than
year-long restoration of the Popper Felix that I owned at the time.

Professionally he was a perfectionist who had a great love for these
instruments.  Personally he was one of a kind with an opinion on just
about everything.  He was with me on the discovery of the machine,
researching its history and working out how to put it back together
with authenticity.  That full story, including comments about Mac and
photos (with an amusing twist at the end) are here:

  https://www.rickcrandall.net/popper-orchestrion/ 
 
If there is a machine where he is now, you can bet it will be playing
perfectly before long.

Rick Crandall
Aspen, Colorado
http://www.rickcrandall.net/