I think this is a guitar speaker (I've always believed that bass speakers are almost always made with ceramic magnets, whereas this seems to have an alnico magnet). I know that Music Man made some ported enclosures, which I usually associate with bass boxes.
What do you think - guitar or bass (or both)? I'd like to buy it for my Fender 75 (which is a 1x15" guitar combo) which is currently speakerless).
Well, it's going to work either way...at the price it's going for now, it's easily worth the risk.
Figure out how much you'd be willing to pay if it was a bass speaker...and let fate decide!
That said, my amps all sound pretty good through my 2 X 15" Sunn Cabinet. Just different...