The full name was Thompson Manufacturing Co. and it was a rare example of an Irish car company. Peter Thompson asked a very famous car designer Frank Costin to design an Irish equivalent of a Caterham Seven. The car featured a much-admired spaceframe chassis housing Vauxhall Chevette engines. Later, Ford engines (84hp / 110 hp / 130 hp) were used. The car had a rather weird aluminum and fiberglass bodywork with standard fixed hard-top and doors opening upwards. This fancy feature made an entry to the cockpit unnecessarily difficult. The TMC Costin was available in kit form and approximately only 26* examples only have been made.

The chassis was later used by the Panoz company.

*Other sources claim 39 examples.