[cosworthfreak]

If it's a GT then it should be CK17. The other Capri codes were 14 for a deluxe (base model) and 30 for an XL.

Maybe a stamping error, do you have any pics? Is it just on the compliance plate, or on the body as well?

The body number on 1970 cars was stamped on the high section of the slam panel, behind the bonnet lock mechanism.

Cheers
Jamie