Luckily, it's not blocked for the blues, however...
I bought this phone at the thrift store, a couple of days ago, for the $6.99 marked price. Why, you might ask, would I want an old rotary phone? Well, I really didn't.
But, I did want the handset. The speaker in the earpiece of the phone produces sound by converting electrical impulses into vibration, which produces the sound you hear on the phone. It will also work in the opposite manner: It will convert vibration into electrical impulses.
The output jack, located on the lower left corner of the body, is relatively subtle. I don't think it detracts from the looks of the guitar, too much.
And, it sounds pretty good through the Pignose amp, in my opinion.