Gould 1 HP K56I Frame Electric Motor, 60Hz, 115 V, 1 ph , 3450 RPM.  As indicated by the K56 frame designation, it has a 5/8" diameter shaft.  The shaft has a key slot.  The motor is quite clean, and in great operating condition; it starts and runs very smoothly with no vibration.  

A bottom mounting bracket is welded to the casing, with four elongated bolt holes, spaced about 3" center-to-center.

Update: I've added a picture of the wiring diagram (last listing photo), as it appears under this motor's wiring box cover.  It shows that this is a dual voltage (115V/230V) motor, with illustration of the wiring connection for each choice.  It also indicates that this motor is not reversible.