You can see the small dial in this picture. Top right of the PFD, beside the top end of the altitude tape.
In the B737NG FCOM (AOM) Vol.2 chapter 10 it is stated:
"Analog Needle (white)
Indicates analog AOA value.
- needle travel is limited to a range of -6 degrees and +21 degrees
- fixed at 0.0 degrees when on the ground and ground speed is less than 80 knots."
The angle of attack indications display ADIRU (Air Data Inertial Reference System) aircraft body angle of attack.