Several days ago I inquired here on MMD on how to tell the difference
between an Ampico A and B roll.  I received one private response from
David Sharpe.  His information was helpful and I thought others might
benefit from seeing what he had to say.  He has given me permission to
reproduce it here.  Thank you, David.

 - - -

You have probably already received other answers to your Ampico A/B
question, but it is a question which has always interested me so here
is my response.

Basically Robbie's suggestion of looking at the crescendos is good.
If the crescendo perforations are identical in treble and bass it is
probably a B roll; if not identical then it is definitely an A roll.
This applies both to the slow crescendo holes (1B and 1T), and the fast
crescendo holes (5B and 5T.)  In this notation the holes are numbered
in from the outer edge with B meaning Bass or left side and T meaning
Treble or right side.  However, I do have several A rolls where the
first 2 or 3 crescendos are identical and you have to look fairly far
into the roll to find differences, so I wouldn't base a decision on
only a couple of synchronized crescendos.

To answer your specific question, the so-called 0B and 0T (zero Bass
and zero Treble) holes are centered just over 1/8 inch from the edge of
the paper.  These perforations are found only in B rolls.  The 1B and
1T holes (the crescendo holes) are centered almost exactly 1/4 inch
from the edge on both A and B rolls.  On A rolls these are the
outermost holes.

The later B rolls often have a string of 6 separate 0B holes before the
music starts -- apparently to make sure the amplifier is in its lowest
setting.  After the initial 6, the 0B holes mostly occur in groups of 3
separate holes.  Longer runs are found when moving the amplifier up or
down quickly.  The 0T holes are almost always made of 3 overlapping
punches which produce short slots.  These slots are almost always
isolated single slots.  I have several B rolls which use no 0T holes at
all.

The B rolls were introduced in November, 1927 and the roll number can
help.  The following are approximate, but pretty close.

The earliest original B ballad roll is 2193 or one or two earlier.
(I have 2151 which is an A.)  The earliest original B classical roll
is 68361.  (I have 68333 which is B, but may be an Ampico recoding and
68323 which is an A.)  The earliest original B popular roll is 209261.
(The next earlier I have is 209233 which is an A.)  All jumbo rolls
(100005 - 101065) are B rolls.

So, with one or two exceptions, any roll with a number greater than one
of these is a B roll.  (A couple of solo piano parts to concertos were
released after November, 1927 and were left as A rolls.)

Confusion arises because many earlier A rolls were recoded to B by
Ampico.  These often have stars on the label, one on either side of the
roll number.  They are usually in a box with later style label, such as
the one with two small red stars in the lower corners or the late Art
Deco label.  Some have no printed indication and you have to look for
0B or 0T holes or synchronized crescendos.  Recutters often tried to
find B copies to recut, but they also copied A rolls.

David Sharpe