I've never seen one like this before any idea what the application is?

tanged on cover with a 1 1/4" hole in the middle. 1 1/4" inlet and outlet. no evidence of any gasket material where the inner door seals against the inlet.

914-6 version.
I don’t know what it would sell for since I never see them for sale but $$$ to a real six owner.

Here’s a thread discussing the difference
http://www.914world.com/bbs2/index.php?sho...&hl=Flapper

And my homemade one