Mark 4 (or IV) Jaguars were built from 1935 to 1949 with a 1-1/2, 2-1/2 or 3-1/2 Litre in-line 6-cylinder engine, depending on the year.
The Mark IV designator was actually applied retrospectively to align with later models, originally the cars were known by their engine size only.
All Mark IV's were built with semi-elliptic leaf springs on solid axles front and rear, and had a seperate chassis/body construction.
The 3-1/2 Litre was introduced in 1938, and was virtually identical to the earlier 2-1/2 with the exception of the larger more powerful engine. The larger engine drank more fuel, not surprisingly.
Now highly collectible, these beautiful Jaguars epitomised the British style and grace of the period.