Studying the Liberation of the French city of Angers in August 1944, I've come across the after action report of the 735th Tank Battalion and the mention of "2 dual purpose 50 mm guns" captured near that city.
The only dual purpose 50 mm gun I can think of is the 5 cm Flak 41 with its primary AA and secondary AT capabilities.
Dual purpose 50mm guns Angers.jpg
Regarding the 57 mm AA gun, I think it is simply a 3.7 mm Flak gun.
Emmanuel
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