Here is a summary of what I've got at the moment:
VANTAGE serial numbers
(electric guitars/basses)
.......1978?/79 V-100 model: "V-100"-sticker, no serial
.......1979 models: VLP Spirit: six digit ser.nos. 05xxxx
........................Vantage Standard (VS): five digit ser.nos. 6xxxx
........................Vantage Performer (VP): five digit ser.nos. 7xxxx
........................Vantage Artist (VA): five digit ser.nos. 8xxxx
........................Ghost (VP 750): no or hard to read (ink stamped) serial
.......1980 (Jan - April): 6 digit serial numbers: 0xxxxx
.......1980 (April) - 1984(June): 7 digit serial numbers, first digit = year of production
........................(1980, 1981, 1982, 1983, 1984)
........................digits 2 + 3 = month of production
.......1980/81: VA900 series: 6 digits: 00xxxx (probably 1980), 01xxxx (probably 1981)
.......1981/82: "Special" series of VP and VA models: five digit ser.nos: 71xxx or 72xxx(VP), 81xxx or 82xxx(VA) (following the number system of
..........................their '79/ '80 predecessors)
.......1984 -1988: letter prefix serial numbers: (A-L)xxxxxx: letter=month, first digit=year of production (unconfirmed!)
.......1990 -1998 (Samick models): no information available (I'm working on it)
What is new?
THE MONTH!
Please check your (7 digit serial number) 1980 - 1984 VANTAGE guitars: digits 2 + 3 is most likely the month of production!
If you've got a (7digit) number stepping out the (01 - 12) line : please let me know!
I strongly believe that Matsumoku stopped building Vantage guitars in 1984.
To look at 1984 serial numbers in terms of "months" will probably tell us if Matsumoku and Chushin were working at the same time for Erikson music, or if there has been a dividing line and a clear transition from uncle Mat to Chushin (or another japanese facility)!