I picked up a Volume Jr. volume pedal from Guitar Center used a few months ago. I noticed that it had a hole in the top and a button switch installed but I didn't pay too much attention until now. The switch triggers the pedal, but there is also a 1/4" jack on the back of it where it says "volume pedal". I am not sure what mod this is or what the switch does. Any ideas?

* it is not another output
Can you take a picture and send it to us? If I had to guess it would be a "true-bypass" switch, as passive volume pedals tend to suck some tone even with the pedal in the toe-down position.