It's a complicated tale.
In 1939 ERA produced the 1500 cc E-type single seater vouturette. There were two chassis, numbered GP1 and GP2 so ERA Ltd were clearly planning ahead for an anticipated reduction in engine size for grand prix racing
Postwar the grand prix formula changed and the E-Type became eligible for grands prix. It wasn't very successful.
So GP2 was fitted with a C-type Jaguar engine and converted into a cycle winged one-and-a-half seater sports car.
In about 1955 GP2 was rebodied by Williams & Pritchard with a Frank Costin designed coupe body.
It was later sold to the owner of GP1 who removed the body and Jaguar engine and restored GP2 as an E-Type ERA. So presumably there are no ERA bits in the car.
Several years later the body was converted to a roadster and was fitted to a Jaguar XK150 chassis.
It apparently has a 3442cc engine although the XK150 had a 3781cc motor
... or so an auctioneer's website says.
So this good looking mongrel is a Jaguar XK150 fitted with a coupe body designed by Frank Costin for fitting to an ERA chassis which has been converted to a roadster.
It was recently advertised as a "Costin Jaguar" but a more accurate description would be "Jaguar XK150 with body by Williams & Pritchard" or "Jaguar XK150 with body designed by Frank Costin" but clearly it wouldn't sell.
