NavList:

Frank.  You asked for dimensions.  See https://airandspace.si.edu/collection-objects/sextant-bubble-aqu-1-a-kollsman/nasm_A19800064000 .  You need to scroll down a bit.  To me, this looks like something knocked up from Kollsman parts for a specialised application where there was insufficient room for the standard sextant and mounting.  This perhaps is the reason why so little about it appears online.  Therefore, I don’t think it’s from a B52, which has plenty of space, except for perhaps a very early prototype with the inline seating arrangement for the pilots.  I think we’re more likely looking for a narrower bodied bomber such as the B45, XB46 (which had a particularly skinny nose with a blob above the guy in the front’s head + they only made one) see  https://upload.wikimedia.org/wikipedia/commons/c/c8/Convair_XB-46_in_flight_061023-F-1234S-022.jpg  , B47, B48, B57, or B58.  The B47 is interesting in that the Co-Pilot seems to have been a jack of all trades; second pilot, flight engineer, rear gunner, and astro shooter.  The Kollsman mounting appears to have been installed in the rear cockpit above the co-pilot’s head see: https://www.bing.com/videos/riverview/relatedvideo?q=walk+around+the+B47&&mid=B7AC8BEB5E473EE2548EB7AC8BEB5E473EE2548E&FORM=VAMGZC  at 12min 43sec.  This might might have required the development of a separate control panel.

It's also possible, but unlikely, that the two parts were originally separated by several more yards of wire than they are now.  In that case, it might be worth looking at the KS39 B58 Star Tracker, see https://www.bing.com/videos/riverview/relatedvideo?q=walk%20around%20the%20B58&mid=6530C1E85F55ED8DAE746530C1E85F55ED8DAE74&ajaxhist=0 at 3min 45sec.  I’ve been unable to find a description, but that must have been quite an early and rudimentary tracker, because I can remember attending a lecture at IC around 1965/6 by the 1963 B58 Tokio to London Flight Captain.  However, the watch holder on the tracking end rules that out.

One possible ploy is to try to identify as many standard Kollsman parts as possible on the item and see where that leads e.g. the stopwatch holder central left and the averager bottom right.  DaveP