The "late Rally" derailleur on eBay is not a prototype. (I've sold exactly this derailleur some month ago to the current eBay seller)
The derailleur is indeed the latest Rally version from 1988. The Rally group was an MTB Group available at the same time as the Euclid group. Most parts have been identical except the more "classic" derailleurs and cranks of the Rally version.
See the pics from Campagnolo's official flyer (September 1988):
http://home.t-online.de/
When I bought it it had a label stating "Campagnolo Touring" but this may have been the shops label.
Dirk "just returned from sunny Mallorca" Feeken
------------ Dirk Feeken Heidelberg Germany
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