Unusual Northern Electric receiver cap

[NorthernElectric]

1st off, I have no recollection of where I got this cap or if it came with the receiver in the photos.  It was in a parts box I put away 5 or 6 years ago and I'm going to put it on a phone I'm in the process of finishing.

The cap has a brass thread insert molded into it and comes with a brass retaining ring with matching threads that screws in on top of the receiver element, a 75Z.  The shell is the same as on the 2 144 receivers I have on other phones, one of which has a 75Z element (the other 144 has a similar unmarked element without the black finish).  Everything seems to fit together perfectly.

Can anyone tell me anything about this cap?  Does it belong with the shell and receiver element?







   

[poplar1]

Heavy duty cap. I believe these were used on pay phones (150- and 160-series) and possibly others.

[NorthernElectric]

Thanks poplar1.

I will use it at least until I get my next batch of spare parts that contains a more typical cap.