Aside from the double-bubble 'hump' where the rear seats ought to be (gone, in the interests of weight-saving), the most obvious difference is the more steeply raked, lower front screen. This can even be unbolted at 'sports events' for an even more dramatic look.
There's also a single-lined hood that Porsche was always keen to point out was merely 'weather protection' and shouldn't be considered as refined or comfortable a hood as the one offered in the ordinary convertible models.
This particular Speedster has amassed a reasonably meagre 36,500 miles and seems clean and straight, but it's hardly a zero-mile time-warp car. And yet you'll need to part with £75,000 to get your hands on it. Compare that with just £25K or so for even a properly mint low-miler (more like £15k if you go for a more doggy example) and you'll see that there's rather a premium on that chop-top look.
There again, perhaps £75K is perhaps a bargain in Speedster terms - we also spotted this one, with a fetching shade of claret for the leather and roof, up for £89,000...