Does anyone know a company that makes a modern credit/cancel unit that
can be adapted to pneumatic operation that will withstand hard service?

Stephen K Goodman - Professional Player Piano & Nickelodeon
Restoration Services
Tarpey Village (Fresno/Clovis) California, USA
http://www.mechanicalmusicrestoration.com/ 

 [ Explanations and pictorial animations are presented at
 [ http://www.coinopgamemuseum.com/mechanisms/coinslide/coinslide.html 
 [ and http://www.coinopgamemuseum.com/mechanisms/payout/payout.html 
 [
 [ The device is known variously as a coin acceptor or coin slide
 [ mechanism or coin payment system; see, for example,
 [   http://www.essexengineering.co.uk/ 
 [   http://www.esdcoin.com/ 
 [   http://www.crowriver.com/ps/coinslides3.htm 
 [
 [ The coin acceptor and coin box must be rugged to resist tampering,
 [ but an external electric (or pneumatic!) up/down ratchet switch,
 [ as in a pinball machine, could credit and debit the coins for
 [ a coin-operated orchestrion.  -- Robbie