Lunar Pilot Chronograph (96B251, 96K111, 98K112, 96A225), Chronograph C (96A283, 96K101) (Add your watch in the comments below…)
The Bulova caliber NP20 is a High Precision Quartz aka HPQ (sometimes written as High Performance Quartz) chronograph watch movement with Ultra High Frequency (UHF) of 262.144 kHz. Bulova refers to it as a 3 eye chronograph movement. It is made in Japan and has 0 jewels.
In Bulova’s own words:
“A movement featuring a 3-pronged quartz crystal with a frequency of 262 kHz that is 8 times greater than standard quartz, leading to an accuracy of seconds a year.” –source
Bulova NP20 VS 8136:
Bulova offers almost no information about their movements. It appears that the NP20 is what they are calling the Bulova caliber 8136 (Citizen/Miyota made). Caliber Corner is still working on getting more information about this, including a hands-on and break down of the movements for photos, etc. In the meantime, you may want to read through the Bulova 8136 caliber listing and the discussion threads over there.
Update: In March of 2023, Caliber Corner acquired this Bulova Lunar Pilot Chronograph watch for the purpose of uncovering the mystery behind the NP20. As it turns out, the watch advertised by Citizen as having an NP20 movement, is actually a Bulova caliber 8136 as suspected above. While the movement itself is signed Bulova, we know that Bulova has been owned by Citizen since 2008 (source). This means the movement is actually a Miyota, since Citzen owns Miyota as well, but specially tuned for Bulova for use in their High Performance Quartz watches.
If it is an 8136 then why do they call it the NP20? Who knows. Short answer: maybe marketing. It could be that they sought to change the name of the movement to NP20 so that it sounds more like a Bulova specific movement, by not using the typical 4-digit Citizen caliber number system. The NP20/8136 is a Bulova-only movement as far as we know, so that makes sense, but what doesn’t make sense is calling the movement “NP20” on their product pages, then opening it up to find a movement marked “8136”. This causes caliber confusion.
Date VS No Date:
With the news of the recent release (February 7, 2023) of the Bulova Lunar Pilot No-Date (refs: 96K111, 98K112), it seemed as if the community would be getting a new caliber number from Bulova – only to find that the movement in the new no-date is called an “N20”, just like the date model. It’s disappointing that Bulova did not come up with a way to distinguish the no-date caliber from the date version (ref: 96B251). If one has a calendar complication and the other does not, then they are not the same movement (assuming that the no-date does not have a phantom date position), and should each have their own caliber designation.