Yes of course it isn't a 73A, that's what happens when you use the Internet and not your own head. The 73A is the little white car that's next to it.
It is a 1952 Bugatti T 57 SC Coupé
Chassis No. 57.561, engine no. 32SC, frame no. 39, Roadster
26/07/1937 imported via Bugatti agent J. Séchaud in Genf (CH), 29/08/1937 custom clearance (no. 9152), delivered to Carrosserie Worblaufen (Fritz Ramseier & Cie.), bodied as roadster with body parts imported from France; 193x delivery to 1. owner Prince Louis Napoleon VI (1914–1997, “Louis de Montfort”), Lausanne (CH); 1938 raced at Course de Côte de Rheineck et La Chaux- de-Fonds, registration VD 19500 (from Bugatti 57GR, chassis no. 57.246, engine no. 129), license GE 2357, 20/08/1938 1st in class (sports cars over 1,500 cc) at Grand Prix Bremgarten with race no. 36, 19/08/1939 1st in class (sports cars over 1,500 cc) at Grand Prix Bremgarten with race no. 10
2. owner André Bordigoni, Genf (CH)
3. owner Riondel
1952 Coupé body fitted by Carrosserie Ghia S.A., Aigle (CH)
195x owner N.N. (USA), engine changed to no. S 1004 (crankcase 57.561/32SC 2003 still in the USA, sump in chassis 57.482)
196x owner John W. Shakespeare (Illinois, USA), colour: green, interior: green and leather; sold with collection of 30 Bugatti cars at 3,000 $ to Fritz Schlumpf
01/03/1964 owner Fritz Schlumpf, Mulhouse (F)
1981 owner Musée National de l´Automobile – Collection Schlumpf, Mulhouse (F) (Günther, Beyer & Prick 1992, Simon & Kruta 2004)
This is the original body being driven by Prince Louis Napoleon VI