Table:
text: Ken Wharton
Complete World Championship results
Complete World Championship results
Year_ Entrant Chassis Engine Points
1952 Scuderia Franera Frazer-Nash FN48 Bristol Straight-6 3
1952 Scuderia Franera Frazer-Nash 421 Bristol Straight-6 3
1952 Scuderia Franera Cooper T20 Bristol Straight-6 3
1953 Ken Wharton Cooper T23 Bristol Straight-6 0
1954 Owen Racing Organisation Maserati 250F Maserati Straight-6 0
1955 Vandervell Products Ltd Vanwall Vanwall Straight-4 0

Question: What was the earliest year for a 3 point cooper t20 chassis car at Ken Wharton?