I suppose it depends on the definition of "major", "museum" and
"depends". But I recall IBM exhibits at Chicago's Museum of Science
and Industry at about the same time that Hammond had a major exhibit
extolling their tonewheel technology for organs. That would be what,
late 1950's, early 60's? I recall a cutaway of a 305 RAMAC as being
part of the exhibit as well as some cool relay-operated pushbutton
exhibits.
When I visited the Deutsches Museum in the 70's, they had already
started accumulating computer gear.
By either of these measures, BCM was a latecomer.
Cheers,
Chuck