John Phillips' questioned as to whether a test roll was produced
for the Half Duo-Art; the answer is 'yes'. I have an example and
on the labels at the ends of the box it has written "Tester for
the 88 note and Duo-Art (foot blown)"
They are, I believe, quite rare. However, it appears to be just
a slightly cut down versions of the standard Duo-Art test roll.
No doubt, someone else will be able to be more specific about the
differences as at the moment I do not have the standard test roll
to compare it with.