The Crosslé 15F is a full monocoque Formula A / Formula 5000 car introduced in late 1968, after the end of the first regular season. Three examples of the model were constructed; two were exported to the USA and one remained in the UK. The chassis was designed to accept either Chevrolet or Ford 5L engines and the gearbox was a DG600 5 speed. Wings were fitted post-factory. The third car is featured in (very) modern trim on the cover of Crowley's excellent book Formula 5000: A-Z.
Note the generally unfinished state of the car in these early magazine shots; first the brief Autosport 1968 mention:
and then the more complete 1985 Autosport Crossle historical retrospective:
Courtesy of Ham Donaldson, a better version of the above picture and the Holywood shop (primitive, by modern standards) from whence it came...
From the sales literature, the top-line specifications: