Notchback rear glass.

Yup, that's a real early '68....Sept 15 1967. the 4 under the lower case b is bucket seats, and Y6 is black vinyl top. It also coded for an AM radio, A/C, turn signal indicators, and tinted glass. If you need the other lower line codes, let me know.
Thanks I sent you I started a conversation with you on here. @cudamark