This is a 1912 patented Trill indicator in it's original box.

Trill Steam Indicator made in Corry, Pennsylvania.  These things recorded the pressure inside a steam engine as the steam entered, the intake valve was closed and then the steam expanded until BDC and then the exhaust valve opened.  Pressure would go up if the exhaust valve closed before TDC.  The information was recorded on a paper card placed in the cylinder with a stylus doing the marking.  Therefore it had a piston operating against a spring that moved with steam pressure and could be calibrated.  A string rotated the cylinder in relation to the rotating of the steam engine.

(Note: Click on a picture for a larger view, then enlarge it through your browser.)