Sorry if I am a little late to this party... I do remember you emailing me and then losing my emails. doh
Panasonic has changed their serial number system a few times over the years which makes it a bit tricky at times.
Most of the 1985 - mid 90's bikes had a number on the lower portion of the head tube. Most were also a number followed by a letter such as 7B09345... which would be Feb. of 1987 (yes, you have to guess the decade based on paint and components but that isn't usually too terribly difficult) Some higher end models such as my Team America had the serial number on the bottom bracket rather than head tube.
Older bikes say from 1984 back to the mid to late 70's would have a couple numbers. Under the bottom bracket or stamped on one of the rear dropouts (rear drops on lower models generally).
The head badge sometimes has four small lightly stamped digits... I believe the first three digits are the day of the year (001-365) and the fourth digit is the last digit of the year.
Your bike being a Tokyo market bike... well, who knows for sure how they were designated. I am still learning myself.
I do think you're on the right track however. Early '92 build with remaining stock of '91 parts.
Founder, Panasonic Bicycles Virtual Museum http://panasonicbikemuseum.info
The Panasonics: 1983 AR-6000 Aero, 1984 DX-4000, 1985 Team, 1986 DX-3000, 1986 Team America, 1986 Team Japan, 1987 MC-6500, 1988 MC-5500, 1988 DX-4000. 1988 DX-5000, 1989 DX-1000, 1989 PICS Team Custom "Lauraire", 1989 PICS Team Custom "NOS", 1989 PICS Team MC-800 Custom, 1989 MC-5500, 1991 PR-6000
The Pinarello: '00 Pinarello Paris