Seat year ID

[Durney]

Hoping someone can ID the year of this seat/cover.

It was in my 74' but the original owner said the cover was replaced by GM (under warranty) "a year or two" after he bought the truck new. You can tell its an original GM seat cover as the construction quality is incredible.

I am having custom upholstery done so I need to know what year to advertise this cover as (knowing it fits likely 73-87 seats of course).

thanks folks.