I found this loose on the floor when I removed the back pad. Sorry about the huge pic, I'm on my phone and don't have an easy way to resize it.

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Yeah, I found one back there several years ago, too, but is light plastic and one corner angled. No one could identify it.

nothing for a 914 that I know of.

My guess is makeshift cover for E brake yoke assembly???

In my case, brake yoke cover in place. Piece had been in there since new as no one had been in behind there until I went in. Sort of covers the seat belt warning relay area but strange holes that don’t align with anything. Keeping it, just in case…..

I'll probably show my ignorance here....again.....but is it possible that this is a tool used on either rear window or backpad installation? Maybe some sort of glue/adhesive/butyl "Spreader/Squeegee".....as just a random possible example. If two people have found them in roughly the same spot, then maybe someone accidently left them?

It's an old American Express credit card. The hole is for your key chain.