This small ad is for a Herstal bicycle fitted with the Paul de Vivie’s ‘système de Vivie’ gearing. This may possibly involve a two speed set up combined with a double chainwheel. It is possible that you swap chainwheels by hand. The gear ratios are (in French terms) 5.40m and 3.50m on one chainwheel and 4.65m and 3.00m (for the mountains!) on the other. In gear inches the equivalent numbers are: 68”, 44”, 58” and 38” respectively. I have seen worse touring ratios.
(Source gallica.bnf.fr/ Bibliothèque nationale de France)