What I'm thinking about is the 17 character standard which came in gradually over 1980. I know that because my 1980 MGB had the 17 digit VIN plate (I always thought it was 16 digit), but some 1979 MGB's didn't. Before that it was a much simpler chassis plate, with variations.
From Wiki...........
Modern VINs are based on two related standards, originally issued by the International Organization for Standardization (ISO) in 1979 and 1980: ISO 3779 and ISO 3780 respectively. Compatible but different implementations of these ISO standards have been adopted by the European Union and the United States, respectively.
