Is box office a proper noun?

Answer 1

No, the compound noun 'box office' is a common noun, a word for any box office anywhere.

A proper noun is the name of a specific person, place, or thing; for example:

• Ticketmaster, main office at 8800 Sunset Boulevard, Los Angeles, CA
• TKTS Discount Booth, Duffy Square on Times Square, New York, NY
• Box Office Mojo, an online movie publication and box office reporting service based in Burbank, CA
• AEG Live, main office at 800 West Olympic Boulevard, Los Angeles, CA