Rob,
It appears that the "shift lever" on the seat tube is used to engage/disengage the generator mounted behind the bottom bracket, see the last picture of the left side of the bike.
Chas. Colerich, Bertin collector Oakland, CA USA
Rob Williams wrote:
> A very nice Bertin on E Bay $500 with a day to go. http://ebay.com/
> Rob Williams
> Sopping wet
> in Seattle USA