As a final note, someone on another forum answered my question about the vintage of Monarch's lifts:
Jamesdeluxe wrote
I walked right up to the plaque to see the date of manufacture but it was rubbed off -- I'm guessing early 1970s?
The answer is: Monarch has four (!) Hall doubles still in operation: built in 1968, 1969, 1980, and 1981 (
map) -- a literal ski lift museum. If I remember correctly, Plattekill's Hall double purchased from Belleayre is from 1977 and similar to Platte, Monarch has no intention of replacing them and no one complains.