been around cars for a long long time. Ya just start to memorize shapes, layouts, wheels, bodylines, little details that makes that car unique and specific to that car's make and model.
I figured it was a bugeye but no way to know for sure if it was modified with a different bonnet.
But, the wheels said British race car all over them, and the door outline was definitely Sprite.
Some take a little more work, like, "oh yeah that looks like it came from this or that manufacture, or designer." Just need to pin down the specific model.
Sometimes it is, "Oh yeah, I seen one of those... what the heck was it agian?"