There were three different types, or "levels", of T-100 rolls created
by M. Welte & Soehne in Freiburg for testing the Welte-Mignon:
"Skala Rolle", "Monteur Skala" and "Fabrik Skala".  Specimens of all
types still exist, and their attributes seem to correlate with the
titles.  I have not myself seen the the rarer styles;  this brief
report is based on conversations with knowledgable technicians and
collectors.

The test rolls entitled "Skala Rolle" (or "Rolla") are not terribly
rare.  After checking the lock and cancel components the tests on the
roll seem to be limited to notefield testing and simple, basic checks
concerning the crescendos and mezzo-forte hook operation.  Since
these rolls were available for purchase from the piano dealer, the
tests did not lead the piano owner (or novice technician) toward any
complicated or critical adjustment procedures, and of course no
specialized equipment was required to perform the tests.  These rolls
were perforated on the familiar red paper.

The "Monteur Skala" test roll ("Installers" or "Assemblers Scale")
was not intended for general use by the public, although it's likely
that some made their way into the hands of the master technicians in
the field.  These rolls were perforated on white lined paper, the
same as used for draft rolls during performance editing.  I don't
know yet exactly how this roll differs from the former, except that
it has more and different tests than the "Skala Rolla"

Only two "Fabrik Skala" ("Factory Scale") test rolls are known to
exist today, and they both display an obvious difference from the
other two types: on Fabrik Skala rolls there are two, and possibily
more, different hole diameters which are used in critical tests.  For
example, one test sequence at minimum expression level strikes the
same note twice in succession, but with different hole diameters.
All playing notes are tested in this way.  A plausible explanation is
that this sequence was for testing the friction of the player stack
and piano action. The note is supposed to sound with the larger hole,
and with the smaller hole the hammer is not supposed to touch the
strings.

One important difference between these three types of test rolls is
probably in the quality control exercised during production.  The
Monteur Skala and Fabrik Skala rolls, punched on the same white lined
paper as used for master rolls, have a significant amount of
pencilled notes added as they were checked for accuracy before being
placed in service.  One can imagine a German artisan testing the
finished hole diameter with calipers or a plug gage, to make sure the
perforator alignment and punch and die set was okay.  The distance
between expression commands and the notes would have been carefully
measured and controlled, too.  This care simply isn't evident in the
commercial production rolls on red paper.

More information is needed about these rolls, and hopefully will be
forthcoming from Europe.

-- Robbie Rhodes  <rhodes@foxtail.com>  13 July 1995