• U19 appears to be an NEC µPD2364, but datasheets of the uPD2364 that I can find show a 24-pin chip, not 28-pin !!!!
In fact, the C version of the µPD2364 is pictured at here, showing 24 pins.
Could it be that in later versions of the µPD2364, NEC upped the pin count and changed the pin configuration to match the Mostek MK37000 ?