Clanad, there are times when I feel old (you too, perhaps) Seeing things advertised as though they belonged in some distant age, does that, as does going around transport museums and seeing exhibits you rode on or drove.
The Solex was a bicycle with a tiny two-stroke engine mounted over the front wheel. You could ride it as a bicycle but could fire up the engine to give a whizzo speed of some, well, 15 mph, without effort. Very popular in France, where it originated, quite a number were sold in Britain