For 1903? Francisco Tamagno portrays ‘L’Impertinente’ (‘the cheeky girl’) sprinting up the Tourmalet using her Terrot transmission with a chain on each side of the frame (and two sets of chainwheels, sprockets etc). This is the transmission that won Terrot the gold medal in the Touring Club de France (TCF) technical trials of 1902. Frank Berto describes it as a 4 speed system with two chainwheels and two sprockets on each side of the frame. Each chain had a hooked link - allowing it to be quickly broken by hand and moved from one set of sprockets to the other. I believe that the rider could choose which of the two chains was doing the driving using some kind of clutch mechanism.
To summarise, you had a choice of two gears based on which chain was doing the driving, and if you got off and swapped the chain onto the other pair of sprockets you could have two more gears. No wonder Terrot were interested in adopting derailleurs!