hehe
that would be if Zupan built any accordions at all
those pretty alpine style, powerful, boxy Zupan's are contracted through Beltuna
afaik, ZUPAN tends to contract in large batches to sell for a multi-year period.
Conditions change and so can choice of Suppliers by the next go-round
if a line or model proved popular. Zupan is very particular in their specs
and may even provide their own privately sourced Reeds for certain models.
Those alpine style wood models that Beltuna built for them were enormously
popular with he Pro's, and are responsive, gutsy accordions to play.
the Pietro was seen around new England some years back, it
does seem to be a stencil brand that could have come from
any number of Italian builders
finding out the builder is of marginal use, really, since the quality
of the build would have been specified by the brands Contracting owner..
not the builder/factory
you could look through older catalogs (this century) as well for
look-alikes, since several companies went out of business in the last
decade or so, they can best be researched by leftover sales materials
and photo's of other accordions.. you gotta dig around the internet