I use a dial indicator to check valve travel.  Enco and MSC or a host
of tool suppliers sell these items.  Enco is probably going to sell
more imports.  They all have dial indicators and depth gauges.  The
inexpensive ones work great in player pianos.

A digital caliper can be bought for less than $50.00.  I use a Brown
and Sharpe dial caliper and love it.  I have used several other brands.

The Enco web site is http://www.use-enco.com/  They also have depth
base attachments for your dial caliper to use it as a depth gauge.

Don Teach - Shreveport Music Co.
Shreveport, Louisiana 71105