I still haven't learned how to completely decode seat tags. Each seat should have one.
I believe the tag identifies the complete seat assembly. 1969 Fastback-Coupe-Convertible Front Bucket Seats were all the same, except the High-Backs used in Mach1-Shelby-Boss and I believe your seat tag identifies a High-Back with the C9ZB-63 engineering number which identifies a Fastback Specific Seat. I can see that you have a Mach 1 and can tell that your seat is upholstered in the Mach 1-Shelby Pattern.
For Instance, a Fastback Rear Seat which is Fastback Specific will have a -63 Number and a Coupe Rear Seat which is Coupe Specific will have a -65 number and a Convertible Rear Seat which is Convertible Specific will have a -76 number.
A Standard Fastback with Head Rest Bucket Seat might have a C9ZB-65 Part Number because it is the same as a Coupe Seat. I'm not positive on that, Just a guess. Everyone feel free to check your seat tags for more confirmation.
Your Tag is also Dated 1 28 69.