Having claimed a famous Argentine GP win two weeks earlier, the Formula Libre Buenos Aires event was used by Mercedes to do further in-race testing.
Held over two 30-lap heats, Fangio would finish 10.5sec behind Giuseppe Farina in the opening round, before coming home second again in the next.
However, once the times were combined a margin of 11.9sec over young team-mate Moss and more than half a minute on the Ferrari of Farina was enough to secure the win on aggregate.
But after the introduction of new short wheel-base W196 thereafter, the streamliner became a rare sight. While it had been mighty at Reims, a circuit with only three real corners, it proved ineffective at tracks with mid-speed and fast turns, having a tendency to understeer.
It appeared at two further races in 1954: the British and Italian GPs, then made a return at Monza in 1955 when the longer-wheelbase chassis 54 was fitted with streamliner bodywork and brought back for Moss, the car running second and setting the fastest lap before the Brit had to retire with reliability issues.
This would be the final world championship appearance for chassis 54. Mercedes withdrew from motor sport activities at the end of the year after the Le Mans ’55 disaster in its driver Pierre Levegh crashed into the crowd, killing himself and 83 spectators.
Chassis 54 remained in Stuttgart until it was donated – still in its stromlinienwagen bodywork – by Mercedes in 1965 to the then-new IMS Museum, where it has remained ever since.
The Mercedes is the first of an 11-car collection being sold which also includes the 1965 Le Mans-winning Ferrari 250 LM and Craig Breedlove’s Spirit of America Land Speed Record contender.
IMS hopes to raise £95m from the combined sale, with the restoration of its museum set for completion in April 2025.
“The Indianapolis Motor Speedway Museum has been honoured to care for and share the W 196 R within our museum, but the sum it has achieved today is a transformative contribution to increase our endowment and long-term sustainability as well as the restoration and expansion of our collection, “said museum president Joe Hale.