The Quadrant no. 21 has full suspension and with all those details and craftmanship it's a marvellous bicycle. Also look at the rear wheel brake. This bike is really a piece of unique and individual design.
At the time when this bicycle was built (Velorama museum thinks 1893) other manufacturers made bikes with pneumatic tires. Also expensive, but I guess not as expensive as all those springs.
Not many of this model no. 21 were built. I read in the magazine of the V-CC that there seem to be five survivors. Velorama has this example with serial number 13693. You found another one in your grandpa's shed? You're a lucky man!