Thank goodness this has been solved! It was pretty obvious the car was not a single-seater - there's enough room in there to hold a cocktail party. Simon Moore the respected Alfa historian also thought it was 412038 renumbered, but changed his mind in a later edition of his history. The car was raced and hillclimbed by Willy-Peter Daetwyler until 1952, when it was rebuilt with the more modern style of body by (reputedly) Michelotti - the idea was to have detachable wings so that he could enter single-seat races and also sports car events.
The puzzle photo was taken 19 July 1953 at the Susa-Moncenisio hillclimb, which he won outright. The "Schlumpf" museum, or whatever it's called now, have the colour scheme all wrong - Daetwyler always painted his cars in the Swiss national colours.