I am not quite sure what a "roadster" was, but surely this must have been one. Mud guards that have the curves of an Impressionist's model, a steering wheel that looks as if it was designed for serious steering, and a running board every young buck would want to jump upon. And within it there is a party going on, and everyone has put their best hat on for the occasion. I suspect that the photograph dates from the mid 1920s, and the rest of the photographs in this eBay purchase were definitely British. Usually you can pin cars down by the position of the steering wheel, but this one seems to be covering all options by having a central wheel.