Graflex XL -WHAT DO THE BUTTONS DO?

[kram]

Help, I have just purchased a Graflex XL (In very good nick with a 80mm f2.8 Heligon lens). The silver button on the front of the camera seems to drop the frame lines to the closest focusing position (is that all it does), but what does the silver button next the accessory shoe do?

 

[kram]

I have found out what the button is. When you chang ethe lens, you push the button to reset the rangefinder to that lens.