The person I picked this up from states that is late Uncle had a bike shop during the mid 80's throughout the 90's. This derailleur plus a few more were stashed away in a box until the nephew was given 'the old bike parts - maybe you're interested' and this one ended up for sale recently. The dude I bought this from didn't have any more detailed information regarding whether this derailleur I have is a prototype or whatever. Would be cool to find an original advertisement or catalogue to confirm prototype or not. Thanks to those who have chimed in thus far!