I think this bike is pre-war. First, compare the lugs, fork blades and crown and rear dropouts with this bike, identified by its Swiss owners as a 1937 No. 7C Weltmeister. Motogeek's bike has the same lugs, just not chromed; what looks to me like the same dropouts and forks. Both bikes have Durax Supercourse cranks with hollow spindles and early Weinmann sidepulls with the wraparound springs rhm described.

The Weltmeister pictured, no. 101370, has its serial number on the left side of the seat tube in the location Motogeek's bike does (and the vast majority of Allegros one encounters). Motogeek's bike is 2,254 earlier than the identified and dated '37 Weltmeister. I earlier pointed out the odd serial numbers and different locations on the '36 and '37 Tour de Suisse models on the speedcycles site, but could those be an early custom shop product, with different procedures? Maybe built so that there were NO additional brazed-on fittings, including the sn lozenges? (The '37 is in original finish with zero braze-ons, the '36 has been repainted and I am not sure of what to think about the brazed-on pump peg).

Then go to the 1940s Allegro catalog here and look at page 9 of the No. 73 Special Sport Extra Light and read the specs - 531, 56cm, 3 speed, two brakes, etc. Then go to the c.1950 Allegro catalog flyer here and look at the No. 72 and 73 bikes on the second page. Finally, go to the 1963 Allegro catalog here and look at the No. 72G Super Luxe. Note that the 1940s and 1950 catalogs mention variable gearing but do not depict it.

Major bike lust here, by the way. That is a beautiful machine!