Although this is a link to T-Bird page it explains the Data Plates were changed during April of '57.
https://www.ctci.org/decoder/
The "Production code" was discontinued and replaced with Transmission and Axle codes.
https://www.ctci.org/wp-content/uplo...02/print03.jpg
The Production code may have had something to do with how many cars of that model were built for a particular sales district.
