You are referring to the promotional 12" single for Overture/Shock Treatment (Richard O Brien version)
I am pretty sure this person is speaking of an actual test pressing of the entire soundtrack album, which would be a much rarer item than the promo 12". A friend of mine just picked one of these test pressings up at a record fare in Chicago as well! I cannot imagine there being very many of these out there so how odd for two to pop up in such a relatively short time. In other words, yes, it is a pretty rare piece.
It's indeed an interesting find. Something I'd like to own. Unfortunately, most have seem to have lost interest in collecting RH merchandise, so, it's not very valuable.
I'd be interested to see scans of the info sheets. As far as the LP itself, well, it's a white label with a white cover. I do not think there is much to see there.
Yikes! Didn't read thoroughly. Thanks. (Sorry for the delayed response.)