Many thanks to SWLing Post contributor, Dan Robinson, who shares a link to this eBay listing of a Hammarlund HQ-180A and notes:
Whoever owned this Hammarlund HQ-180A installed a DC meter where the clock or crystal unit usually is.
And the screws on the top of the hatch seem to indicate installation of a DC supply perhaps?
Like you, I’ve never seen this particular mod to the HQ-180A, Dan.
I’m curious if the owner installed the DC meter to replace a broken or missing clock? Though I’ve never searched for one, I suspect those Hammarlund clocks are getting more difficult to find on the used market.