That sounds right to me, Paul. The earliest 100 Sport I've come across is 20M-00200 from January 1967, and the latest is 20Z-12370 from December 1967. Factory production figures suggest that round 18000 of examples were built, so that suggests production would have carried on for a while into 1968.
Has anyone got a 100 Sport with a number later than 12370?
Graham