Over the years I have tuned two or three transposing pianos carrying
the name James & Holmstrom.  In order to overcome the splits caused by
the action brackets and plate struts, the keys are practically straight
rather than offset as in standard pianos.  The offset is built into the
stickers so that there is a uniform spacing from #1 to #88 to match the
keys.

If I remember correctly, there are more than 88 keys and the unused
end keys simply slide under hollow key blocks.  The action brackets
are offset to run behind the stickers.  Beneath the keybed is a capstan
wheel which is geared to slide the key frame left or right.

Unfortunately, all the James & Holmstrom pianos I have ever seen had
separating pin blocks.

Bill Maxim