Julie Porter noted that the offset drum holes on the Wurlitzer 165
tracker bar are different holes than on the APP and Caliola tracker
bar, and that the Wurlitzer 165 at Glen Echo Park, Maryland, has
Caliola tracker bars.

The Glen Echo 165 has Caliola bars because it was converted to Caliola
rolls, probably by T.R.T., in the late 1940s or early 1950s.  When
Durward Center restored the organ and re-converted it to 165 rolls in
1978, the Caliola bars were left in place.  So the drum perforations in
the 165 roll pass over holes that are not offset, but, interestingly,
the drums do not beat late.

This raises the question of whether Wurlitzer's offsetting of the holes
was ever necessary.  Though the original 165 tracker bars were replaced
with Caliola bars, it seems it was not necessary to do so, given their
apparent interchangeability, just as it was not necessary later to
return to 165 tracker bars (which was not done).

Much of this was originally delineated by Matthew Caulfield in MMD
98.09.21, but I believe it bears repeating in the context of the
current discussion.

Dan Robinson
Rochester, New York