[CR]Cambio corsa drop-outs

I believe it has been determined that the Campagnolo 19 tooth drop-outs were designed specifically for use with the Cambio Paris-Roubaix (In italy also known by the translated Parigi-Roubaix name). When going over a frame that I have in my garage that came to me with a Paris-Roubaix gear, I have found that it has drop-outs with 17 teeth and a front hub 'stop'. You can see a photo here: http://www.wooljersey.com/gallery/Cambio-corsa-frames/Red_rear_dropouts?f ull=1

Somewhat curious as to whether the Paris-Roubaix was original to this frame or 'upgraded' later, I have searched for information. I have been able to find a few photos of late 40's bikes with this style drop-out and the Paris-Roubaix derailleur (then not yet known as Paris-Roubaix as Coppi had yet to win the race with this gear), as well as a page in an early 1950's Bozzi catalog. I was therefore wondering when did Campagnolo begin producing the 19 tooth drop-outs? Was the drop-out witht he hub stop also used with the cambio corsa?

Steven Maasland
Moorestown, NJ