[Collins] Early 75A-4 rejection switch question

[AI2Q]

My 75A-4, which I have recently repaired and restored, has an early 
three-digit serial number. My question has to do with the Q-multiplier. The 
Rejection Tuning knob switches the filter in and out; the OFF position 
engages a silver tab that touches what looks like a small contact on the 
front facing portion of the filter can.

Is this switching scheme something common to all 75A-4 receivers, or just 
the early ones?

Any comments much appreciated.

Vy 73, AI2Q, Alex