The side knobs just pry off. There may also be a white knob on the back marked "peak picture". Pry that off too.
The side knobs sometimes are captive so they will just hang off. Dont
forget to remove any wires from the antenna terminal board.
When opened you can get the chassis number. Its usually on a tag
pasted to the HV cage. Its what we go by as a rule.
73 Zeno
LFOD !