Controls: Top Left - Rotary Tone; Bottom Left - Rotary Acoustic Filter; Middle - Pickup Selector Switch; Right - Rotary Volume. This particular guitar does not have the Push-Pull Preamp Boost facility on the volume knob that most S5PA guitars have.
Note the chrome cover for the battery compartment adjacent to the strap button.
The PCB for the Acoustic Filter is mainly visible in this photo. Note that it is marked for the S7 solids for which the Acoustic Filter was developed, a year before the S5PA was introduced using the same feature.