With the current-generation Porsche 911 (991 Series) set to be replaced with an all-new model (992 Series) next year, the German carmaker is preparing a grand send-off in the form of the 911 Speedster for the 991 Series.

Here it is as captured by our spies, and it will be the fourth 911 Speedster produced after the 930, 964 and 997 generations. As far as we can tell, the test mule looks almost production ready, and it shouldn’t be too long before it makes its global debut.

While it may look like a typical 911 Cabriolet at first glance, the fitment of the fabric top on this mule looks a little awkward and likely masks the design changes beneath. Expect a lowered windscreen and a manual ragtop to be part of the Speedster’s feature set – a throwback to the original 356 Speedster like the previous 997-based Speedster.

Like that model, the new one will be built in limited numbers, which could be 1,948 units to celebrate Porsche’s 70th anniversary this year. The previous Speedster saw just 356 examples being built, by comparison.

Our spies claim the mule here is powered by a 4.0 litre naturally-aspirated flat-six engine, given the presence of a 911 GT3 RS in the convoy. There’s also a likelihood that the 3.0 litre turbocharged flat-six from the 911 GTS will be used, but we’ll have to wait to find out.

The Speedster project should be handled by Porsche’s Exclusive department, with the 997-based Sport Classic being another one of its creations. Expect it to cost more than a pretty penny, and be highly desirable among car collectors.