(Jon of the Clue Crew reports from Steinway and Sons.) It's the ten-letter term for the piano's diaphragm; it's made flexible enough to vibrate, but strong enough to handle a thousand pounds of force from over 200 strings
I assume its a 
calculation of the totals of measurements made on each ... (probably not) 
Measured force needed to deflect the strings a ..... 1000 Post Club Member [DOC] [TLE] Full text of "Cassier's magazine" - Internet Archive [PAR] Further on the way, to Plainfield, no noteworthy speed was made, but there were, 
......