Anybody seen this before?

It is more likely that the seat is from a 1974 model.
In 1974, there was a series of electrical connections that were all part of the Federally mandated Seat belt/Starter interlock system. The cars of 1974 could NOT be started if the system sensed weight (Persons) sitting in the seat without the seat belts connected. The thin, shiny metallic strip confirms that the seat is part of that system.
Up to 1974, the seat belt warning light (IF equipped) was merely a warning and it went out on its own with no additional action. The same 70-73 light returned in 1975 and 1976 since the 1974 system was plagued with complaints by angry customers