John Tuttle has just provided me with a photograph that makes it
definitely clear that the tool he first inquired about is, indeed,
a three-needle hammer voicing tool, so I stand corrected about my
previous suppositions.

The details in this most recent photo, which were not shown in his
original photo make clear the position of the needles and the their
retention method.  I expect he will subsequently share this photo with
MMD readers.  Thanks to John for an interesting little mental exercise
and I welcome the opportunity to increase my knowledge on the subject.

John Grant