Marcelo, I'm pleased you at least received a reply, which is more than the silence that greeted my email.
I am convinced that this camera cannot possibly be a genuine E3 prototype. Why would any manufacturer, especially one with the engineering ability and model line of Rollei, use a Rollei T as a prototype for an E3? Rollei had already produced a 2.8 E and a 2.8 E2 that could have been used as the basis for any prototype E3. At least this would provide the lens board designed to accommodate the 2.8 lens. The Rollei T and 2.8 E range of cameras could not be more dissimilar, with the former having a f3.5 lens, different shutter release, position of the flash socket and a totally different mechanism for enabling the shutter speeds and apertures to be seen at the top of the viewing lens housing.
My guess is that someone at Rollei had completed the assembly of a T from odd bits from the parts bin. Whatever the reason or whatever the seller was told, I am surprised that any experienced dealer would present this camera to market at the asking price shown, when a modicum of research would sound some very loud alarm bells.
Nevertheless, an interesting Rollei listing!
Ray