Ask a gearhead what they think is the greatest Subaru built and the answer is probably something related to rally Imprezas – unless you're talking to a more quirky sort who'd throw out the SVX, XT or the bed-mounted jump seats of a Brat. But in any case, the 1990s rally Subarus are great, their road-going versions are brilliant and the rarest of all is the bulging 22B, which commands strong money due to its very limited availability.

The Impreza 22B, reportedly named so for its 2.2-liter turbo boxer, but which also refers to the hexadecimal value of 555, Subaru's rally sponsor, was a widebody special with a bigger engine and more STI magic than other WRX variants. Officially it had 280 horsepower, but almost every Japanese performance car was advertised with that amount at the time – true figures take a dyno run or a dedicated mind to uncover. In addition to the modified body, the suspension was 22B-specific, as was the aero. The 2,800-pound 22B took just 5 seconds to hit 60 mph, a strong feat for 1998, and on the right road with the right kind of driver it is likely to be unparalleled for its era.

As rare as any 22B is, there are also Subaru-built prototype cars that weren't part of the initial 400-car Japanese production run or the official 16-unit UK-bound batch, or the five Australian market cars. Some sources say there were 424 22Bs made, some mention a different number, and the prototypes are understandably the most coveted, least obtainable ones.

Which brings us to this car currently for sale, which just so happens to be one of three known "000/400" series prototypes with just 55 kilometers (34 miles) on the digital odometer. Is this an actual wheeled unicorn?

Contempo Concept, the Hong Kong-based dealer that also stocked the Miata Roadster Coupe we featured, has provided precious little information about this particular car, other than some very good sales photos that show the 22B in mint condition, complete with the 000/400 prototype plaque. There's no mention of the price – this Subaru is likely to have entered the "If you must ask, you cannot afford it" class of cars. It's not immediately obvious whether its prototype status would make it difficult, if impossible to register on the road, and/or if the low odometer reading is due to the car being more of a display item in the legal sense.

22B values have risen sharply during the past decades, and the prototypes will be the most expensive. As an example, Bonhams sold a Japanese-spec 22B in 2010 for $34,000, and in 2017, it auctioned a rally-liveried prototype for almost $150,000. It's entirely possible that the 22B here can break $200,000. And for a unicorn prototype, it's perhaps even justified.