This just promted enough passing interest for a few minutes on the Google as these kind of posts sometimes do with me, but it seems pretty simple...there were two similar looking Ampeg cab models: the SVT 215E and the SVT 215GLS, with differences that are primarily internal. The 215E was a regular production model (though not particularly popular) over a span of years, while the 215GLS was a limited run specialty model with some specifically unknown number made...in the mid to high tens.
Looking at the used market over 25 years after the 215GLS was made and 20 years after the 215E was discontinued, 215Es are out there but less than common, and the 215GLS genuinely rare.
The seller saying it "looks like a Gene Simmons model" is...err...fair. Visually, it does...because the Classic and Gene Simmons models look similar. Technically true statement by the seller...
Since the cab up for sale is clearly labeled "215E", and we also know that there are also correctly labeled 215LGS cabs, does it make more sense to think that this is a mislabeled 215LGS (increasing its rarity significantly) or just a correctly labeled 215E? Considering there’s nothing out there in the way of tales of mislabeled 215LGS cabs, that's pretty easy to answer for me.