[ Ref. Harold Ball in 241202 MMD ]

Harold mentioned the presence of a couple of rotary discs used for
dynamic control on his Duo-Art.

I've never seen those on later Duo-Arts; the closest thing I've seen
to that would be the Temponamic knobs on Steinway Duo-Art grands from
the earlier '20s.

I'm no expert but that sounds like an earlier feature [installed] on
a later-style piano, which is odd.

Piotr Barcz
Upstate New York