Continuing my email discussion with Nicolas Lutz, grandson of Arnold Grandjean, Allegro founder: here are a couple nifty pictures, with his descriptions:
1. http://www.nonlintec.com/
Just a few family photos. This is Arnold Grandjean crossing first thé line of the Swiss cross country championship on April 17, 1915 on a Condor bike. Allegro came later. On of 7 brothers ... my grandfather developed Allegro during the 2nd WW. Each brother took an active part in the business. The bikes were made in Marin near Neuchatel and renowned for their quality finish until the 70's. I suspect yours being from around 1970, maybe a bit before.
2. http://www.nonlintec.com/
One of the few tendems Allegro made in the 50s with Mr and Mrs Grandjean enjoying a ride.
Steve Maas
Long Beach, California