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Serial #'s are now on the lower left of the headtube, by the Schinn badge on fromt of the frame

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Numbering system:

The first letter is the month, the second letter is the year.
I and O are skipped so as to avoid confustion with 1 and 0.

Examples:
AF***** = Jan. 1970,..... ("A" = Jan., "F" = 1970)
GL***** = July. 1975,..... ("G" = July., "L" = 1975)
MR***** = Dec. 1980,..... ("M" = Dec., "R" = 1980), etc.
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(1970)

JANUARY, ---------------------------- AF*****
FEBRUARY, -------------------------- BF*****
MARCH, ------------------------------- CF*****
APRIL, --------------------------------- DF*****
MAY, ----------------------------------- EF*****
JUNE, ---------------------------------- FF*****
JULY, ---------------------------------- GF*****
AUGUST, ----------------------------- HF*****
SEPTEMBER, ------------------------- JF*****
OCTOBER, --------------------------- KF*****
NOVEMBER, ------------------------- LF*****
DECEMBER, ------------------------- MF*****

(1971)

JANUARY, ---------------------------- AG*****
FEBRUARY, -------------------------- BG*****
MARCH, ------------------------------- CG*****
APRIL, --------------------------------- DG*****
MAY, ----------------------------------- EG*****
JUNE, ---------------------------------- FG*****
JULY, ---------------------------------- GG*****
AUGUST, ----------------------------- HG*****
SEPTEMBER, ------------------------- JG*****
OCTOBER, --------------------------- KG*****
NOVEMBER, ------------------------- LG*****
DECEMBER, ------------------------- MG*****

(1972)

JANUARY, ---------------------------- AH*****
FEBRUARY, -------------------------- BH*****
MARCH, ------------------------------- CH*****
APRIL, --------------------------------- DH*****
MAY, ----------------------------------- EH*****
JUNE, ---------------------------------- FH*****
JULY, ---------------------------------- GH*****
AUGUST, ----------------------------- HH*****
SEPTEMBER, ------------------------- JH*****
OCTOBER, --------------------------- KH*****
NOVEMBER, ------------------------- LH*****
DECEMBER, ------------------------- MH*****

(1973)

JANUARY, ---------------------------- AJ*****
FEBRUARY, -------------------------- BJ*****
MARCH, ------------------------------- CJ*****
APRIL, --------------------------------- DJ*****
MAY, ----------------------------------- EJ*****
JUNE, ---------------------------------- FJ*****
JULY, ---------------------------------- GJ*****
AUGUST, ----------------------------- HJ*****
SEPTEMBER, ------------------------- JJ*****
OCTOBER, --------------------------- KJ*****
NOVEMBER, ------------------------- LJ*****
DECEMBER, ------------------------- MJ*****

(1974)

JANUARY, ---------------------------- AK*****
FEBRUARY, -------------------------- BK*****
MARCH, ------------------------------- CK*****
APRIL, --------------------------------- DK*****
MAY, ----------------------------------- EK*****
JUNE, ---------------------------------- FK*****
JULY, ---------------------------------- GK*****
AUGUST, ----------------------------- HK*****
SEPTEMBER, ------------------------- JK*****
OCTOBER, --------------------------- KK*****
NOVEMBER, ------------------------- LK*****
DECEMBER, ------------------------- MK*****

(1975)

JANUARY, ---------------------------- AL*****
FEBRUARY, -------------------------- BL*****
MARCH, ------------------------------- CL*****
APRIL, --------------------------------- DL*****
MAY, ----------------------------------- EL*****
JUNE, ---------------------------------- FL*****
JULY, ---------------------------------- GL*****
AUGUST, ----------------------------- HL*****
SEPTEMBER, ------------------------- JL*****
OCTOBER, --------------------------- KL*****
NOVEMBER, ------------------------- LL*****
DECEMBER, ------------------------- ML*****

(1976)

JANUARY, ---------------------------- AM*****
FEBRUARY, -------------------------- BM*****
MARCH, ------------------------------- CM*****
APRIL, --------------------------------- DM*****
MAY, ----------------------------------- EM*****
JUNE, ---------------------------------- FM*****
JULY, ---------------------------------- GM*****
AUGUST, ----------------------------- HM*****
SEPTEMBER, ------------------------- JM*****
OCTOBER, --------------------------- KM*****
NOVEMBER, ------------------------- LM*****
DECEMBER, ------------------------- MM*****

(1977)

JANUARY, ---------------------------- AN*****
FEBRUARY, -------------------------- BN*****
MARCH, ------------------------------- CN*****
APRIL, --------------------------------- DN*****
MAY, ----------------------------------- EN*****
JUNE, ---------------------------------- FN*****
JULY, ---------------------------------- GN*****
AUGUST, ----------------------------- HN*****
SEPTEMBER, ------------------------- JN*****
OCTOBER, --------------------------- KN*****
NOVEMBER, ------------------------- LN*****
DECEMBER, ------------------------- MN*****

(1978)

JANUARY, ---------------------------- AP*****
FEBRUARY, -------------------------- BP*****
MARCH, ------------------------------- CP*****
APRIL, --------------------------------- DP*****
MAY, ----------------------------------- EP*****
JUNE, ---------------------------------- FP*****
JULY, ---------------------------------- GP*****
AUGUST, ----------------------------- HP*****
SEPTEMBER, ------------------------- JP*****
OCTOBER, --------------------------- KP*****
NOVEMBER, ------------------------- LP*****
DECEMBER, ------------------------- MP*****

(1979)

JANUARY, ---------------------------- AQ*****
FEBRUARY, -------------------------- BQ*****
MARCH, ------------------------------- CQ*****
APRIL, --------------------------------- DQ*****
MAY, ----------------------------------- EQ*****
JUNE, ---------------------------------- FQ*****
JULY, ---------------------------------- GQ*****
AUGUST, ----------------------------- HQ*****
SEPTEMBER, ------------------------- JQ*****
OCTOBER, --------------------------- KQ*****
NOVEMBER, ------------------------- LQ*****
DECEMBER, ------------------------- MQ*****

(1980)

JANUARY, ---------------------------- AR*****
FEBRUARY, -------------------------- BR*****
MARCH, ------------------------------- CR*****
APRIL, --------------------------------- DR*****
MAY, ----------------------------------- ER*****
JUNE, ---------------------------------- FR*****
JULY, ---------------------------------- GR*****
AUGUST, ----------------------------- HR*****
SEPTEMBER, ------------------------- JR*****
OCTOBER, --------------------------- KR*****
NOVEMBER, ------------------------- LR*****
DECEMBER, ------------------------- MR*****

(1981)

JANUARY, ---------------------------- AS*****
FEBRUARY, -------------------------- BS*****
MARCH, ------------------------------- CS*****
APRIL, --------------------------------- DS*****
MAY, ----------------------------------- ES*****
JUNE, ---------------------------------- FS*****
JULY, ---------------------------------- GS*****
AUGUST, ----------------------------- HS*****
SEPTEMBER, ------------------------- JS*****
OCTOBER, --------------------------- KS*****
NOVEMBER, ------------------------- LS*****
DECEMBER, ------------------------- MS*****

(1982)

JANUARY, ---------------------------- AT*****
FEBRUARY, -------------------------- BT*****
MARCH, ------------------------------- CT*****
APRIL, --------------------------------- DT*****
MAY, ----------------------------------- ET*****
JUNE, ---------------------------------- FT*****
JULY, ---------------------------------- GT*****
AUGUST, ----------------------------- HT*****
SEPTEMBER, ------------------------- JT*****
OCTOBER, --------------------------- KT*****
NOVEMBER, ------------------------- LT*****
DECEMBER, ------------------------- MT*****

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During the 1980s, Greenville used the old letter-digit
(e.g. F8 = June 1988) system which Chicago stopped using in 1965,
changing to the two-letter system.

For newer bikes:
there's a 4 digit serial number lightly stamped onto the headbadge.
The first three digits are the numerical day of the year,
and the last digit is the last digit of the year.

Example:
3654 is 12/31/84 or 94 or (?).