Question(s) about blank-backed 'E96s'

[Rob D.]

It is pretty much accepted (I think) that the blank-backed "cards" that resemble E96s actually were cut from notebook covers from the same era.

Below is a scan of one of the notebooks, which I have in my collection. Also shown is an individual, blank-backed "card" I recently picked up, which I first thought was cut from a notebook cover. My question stems from the fact that the paper stock of the cover of the notebook is noticeably thicker than that of the individual "card."

Has anyone seen a notebook cover of different design that has images of the E96s? I ask because perhaps that cover is thinner than the one on my notebook. Or, is it possible that some examples of the individual "cards" came from another source? My example certainly is not a blank-backed E96, because it's simply too thin. It likely was cut from a cover; I'd just feel better accepting this if the stock were thicker.

Thanks for any input.

Rob