Is it supposed to have a gasket or not?

I was always under the impression there was only sealer/no gasket was used on the 1969 Plymouth B body rear window.

You can imagine my surprise when, after 30 years of ownership I popped the back window out of my '69 GTX to find it installed with a gasket under it, but spacer blocks/sealer on top of it.

Was that a hacked installation/some slob's idea of a repair, or were any of them actually made that way?

My thinking: If it's supposed to have a gasket, it's a little odd that nobody sells one.

(I haven't got as far as checking glass date codes, but that might help explain part of it)

thanks