Pantographed derailleurs are unusual, but they are out there. Here you can look at a small sampling:
Kurt Sperry Bellingham, Washington USA
On Tue, Jun 1, 2010 at 12:51 AM, donald gillies <gillies@ece.ubc.ca> wrote:
> http://ebay.com/
>
> [Description] A PATENT-78 Nuovo Record derailleur with the moderne
> MASI name down the front of the derailleur body, and italian colors on
> the upper shoulder and around the lower pulley outer plate.
>
> It's the only pantograph rear derailleur I've ever seen !! generally,
> pantographing was applied to wide expanses of flat aluminum, and a
> nuovo record derailleur really has NO flat aluminum to start, so it
> must have been a real PITA to make !!