Label on window frame reads "M.B. Type 1 Standard". Cream steel panels, glass window, 4 jack panel below window, burl laminate fold down shelf, power cord on top. It's an IAC (Industrial Acoustics Company) booth. Its "M.S. Type 1 Standard" label most likely stands for an IAC Mini Sound Shelter, the 250 series. Certainty: Medium. The nameplate's old Bronx address and (212) phone number suggests the booth is several decades old.
Two likely models
252 Mini Sound Shelter (best match for "M.S.")
254 Mini-Max (close sibling)
Outside size (W x D x H)
29" x 39" x 75.5"
36" x 41" x 75.5"
Weight
650 lb net, 710 lb shipping
890 lb shipping
Fits through
Any normal 30" door, shipped assembled
Any normal 32" door, shipped assembled
Jack panel
6 jacks (yours has 4, so it may be an older version)
Not stated
One tape measurement settles which one it is: the narrow side is either about 29" (252) or about 36" (254). My estimate from your photo (36" to 40" across the window side) fits the 252's 39" depth, which suggests the window is on its long side.