1964 dated case with a 1966 dated movement. Thirty jewels, black dial with the date at 4 O'clock, automatic 10CRACD.
The only 30 jewel movement with the date at 4 O'clock that I can find is the Date King 'NS', which has what looks like a similar case (doesn't have a gold plated case back), with a similar dial (doesn't have two lume pips above 12 O'clock, square lume pips elsewhere instead of round). So not sure what to make of it, possibly a frankenwatch, possibly a re-dial...
I'm fairly certain that your watch is part of the Bulova Date King series. It's possible the case is not original to the movement and dial (or vis-versa).
As it stands at the moment I'm leaning towards an ID of 1966 Bulova Date King, based primarily on the movement and dial combination and styling.
I pondered this one for a long time and found nothing in the linebooks (1964 - 1967) or the database.
The first mention we seem to see of the 30J movement with date window at "4" position in Bulova literature is 1967, with known examples dated 1966, which makes sense. 1967linebook165 page 26 shows the Date King "NS" for the first time. Directly above it, the watch illustration and description have been cut out and are gone. Was this removed watch a charcoal dial "4" window watch with a gold back? We will likely never know.
Subject watch looks like it's a factory dial, but I find no mention of charcoal/black variants.. Dial appears to have been rendered it's color before the indices and date window were applied and is the same configuration as the "NS" with the exception of the lume pip shape.
Case appears to be the same as the "NS" except with a gold back with a mismatched date.
There is a good possibility This is either a legit unidentified 1966 Date King with a switched back or a surplus back made it's way onto the assembly floor. It may also be a 1966 dial/movement combination transplanted into a 1964 case that's the same as the original.
Based on the above observations, I agree this one should be dated by the movement and dubbed
1966 Date King - no variant.