Here is my vintage late-50's/early-60's Morrison 14" diameter standard elevator fan but is unique in that it has a 4-blade propeller that is less common than both 3 (and especially 5) blade propellers. Also, it has the very nice winding up, quiet effect on low speed, the quiet but powerful effect on high speed, and because of the unique 4-blade design, this might have come from an old Otis elevator. However, I wonder why 4-blade fans are so rare, even though they look nice, are powerful, and appear to have balanced blades.

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