[Milsurplus] ARB Antenna capacitor

[Hue Miller]

http://www.ebay.com/itm/WW-II-NAVY-AIRCRAFT-RADIO-RECEIVER-TYPE-CRV-46151-HAM-RADIO/251398161407?_trksid=p2045573.m2102&_trkparms=aid%3D555012%26algo%3DPW.MBE%26ao%3D1%26asc%3D298%26meid%3D3260273197038747044%26pid%3D100034%26prg%3D1079%26rk%3D5%26rkt%3D8%26sd%3D141043077207%26


or by item title:  WW II NAVY AIRCRAFT RADIO RECEIVER TYPE CRV-46151 HAM RADIO 

or by item number  251398161407

Which is fair condition ARB with local tuning crank, with spinner post broken off. 
But what interests me is the large mica cap attached where the antenna connector
should be. 
In  the past I have seen one out here on the opposite coast with exactly the same
type capacitor in the same position. So was this in place merely to replace a broken-off
antenna connector, or is there some more arcane purpose to it?
-Hue Miller