I showed a 1960's Cinelli at VR this year, a pista frame with a derailliur tab added in 1968 or so (and cantilever bosses - strange history on this one!). Have had more than one person remark that it was not uncommon to see derailleur tabs on old Cinelli track frames. I've never seen one, however.
The tab on the Paramount looks so well done, even chrome, I would guess it was done as a custom order. Not being a frame designer or builder, I wonder where is the best location for the tab? The one on my Cinelli is located a bit further forward. Great chain wrap, delicate wheel removal process...
Oh yes, imagine all the rings on the drop-outs reflect many gearing changes on this bike over the years.
John Siemsen SLO, CA