I'll try to look at my 59 in the next day or so. The way it latchs is the tip on the knob looks like a bent over screwdriver tip. it engages the spring metal peice and hooks. When you turn the knob it spreads the spring metal to alow it to release.
I'll have to look at mine to see how the knob attaches to the mounting plate. It's probably a c-clip on the back side. If so a sharp pair of needle nose plyers will take it off.
1959 22' Caravanner
1988 R20 454 Suburban.