Sir Micro9 . . . .

Since this is a "day one" FM receiver design, it is not incorporating the later forthcoming AFC tuning correction to the FM local osc section.

That sort of resembles a Centralab or Erie ceramic capacitor, when blowing up the Sams photo.

In my encounters with them they usually had the cap values stamped in black ink on the sides of a unit.

What might be real tricky was the possible potential of the use of a temperature compensated unit !

Therefore . . . How about fill in details for the unit . . .

.
Is it cannabalized and missing . . . . Does it seem to be physically broken . . . .or ?

Since it is shunting the FM variable tuning condenser, its function is to variably and selectively "squeegee" the maximum capacitance
availability of the summed capacitance of it and the osc sections variable capacitor.

It will primarily be associated with accomplishing the HIGH end tuning tracking on the FM band while its companion the oscillator coil,
with its adjustable tuning slug will be associated with accomplishing the LOW end tuning tracking.

Try the unit out as it is now and see how close a station at ~ 106 Mhz is coming in, and how close it is being in sync to the dial scales
calibration.

E.G. if a station at 105.3 is coming in at a dial scale reading of 107.1 . . . . more capacitance is being needed in circuit by that capacitor C7
. . or T(rimmer) 7 adjustment. Or vice versa, less capacitance, if 105.3 is treading out as 104.

I would suspect the cap value to be in the order of ~2 pf min thru 7 pf max.

If your unit is totally missing the trimmer cap , you might start with a solid ~18-20 ga hook up wire with its plastic insulation and hand fabricate yourself a "gimmick" cap
as shown.

The splayed out end tabs then let you use an inserted HDPE plastic "orange peeler" to "knife in" and gradually unwind turns to decrease capacitance
with minimal capacitive or hand detuning effects.

When I get one optimized, I pull the unit and place my digital cap meter in its low pf range.

Touch one cap meter lead firmly to the gimmick cap and bring the OTHER cap meter up to within .0000000000003 of an inch of touching
the other lead and then freeze any hand movements to check the meter to read the "laid out test lead stray capacitance" . . and memorize.

Then micro wag in that second meter to then touch the gimmicks other lead and read the slight increase in capacitance.

Subtract the first reading from that, any you will then be at the cap of the gimmick.

Ilustración . . . Le "gimmick" capaciteur . . . .

For final testing of overall oscillator stability, you can tie in DC metering into the Ratio det Zeroing adjustment, leave it connected, and then see if there actually IS any osc drift problem with warm up .

73's de Edd

Statistically, 6 out of 7 dwarves are not Happy.