Hello all, I have seen this tracker bar before, installed in an
English Weber, and I think I have another one in my bone yard of parts.
So what is it?  I believe this was a tracking device that worked better
in theory than it did in actual use.  Hence the tracker ears which were
also in the Weber I saw years ago.

My guess is that the twin holes over the center of roll travel was to
bleed out the twin bellows tracker in case one series of holes covered
up the other side thereby shifting the top spool.  Note the two long
slots line up with a single note hole.  I'm reasonably sure that is what
it was meant to do.  However it would have been an extra long bit of
tubing to make it function as opposed to the simple left/right ears that
Aeolian liked best.

Although the preceding is my own personal speculation I will gladly
stand corrected should anyone else (especially on MMD) have any other
explanation!

Eric Shoemaker