FX Wildcat Air Tube O-Ring Question

I found the slow leak in my Wildcat Mk2 - it had a slice in the o-ring in the gauge end of the air tube. See red circle for location of sliced o-ring.

When I disassembled, I noticed a second “groove” that has no o-ring installed. (See white circle for location at very front of threaded area).

As I purchased this Wildcat used, I’m not certain of its o-ring maintenance history…

Question: should there be an o-ring installed in the location I circled in white?

(If yes, does anyone know the size of this o-ring)?

Thanks,

-Ed

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