This latest prototype is wearing the same amount of camouflage as the car spotted last month on public roads.
The spy photographers did manage to get a few snaps of the A-Class' interior, and unlike the car spied in February, this vehicle had its protective sheets rolled back.
These latest images reveal an interior design inspired by those used in the C-, E- and S-Class ranges, although it's not a scaled-down copy. In the centre of the cabin are three circular vents underscored by a climate control pod.
Linked together by a piano black covering is a digital screen ahead of the driver and an infotainment screen in the centre dashboard. These screens are smaller than those used in other Mercedes-Benz vehicles, and it's not clear if they are temporary units or something close to the final product.
Under the skin, the next-generation A-Class is expected to use the new MFA2 platform for front- and all-wheel drive vehicles.
Over time, the MFA2 platform will be used for the next-generation B-Class, GLA, CLA and A-Class sedan. The latter was previewed by the Concept A at this year's Geneva motor show, and will give the company a competitor at against the Audi A3 sedan in the vital Chinese and American markets.
In addition to a selection of turbocharged four-cylinder petrol and diesel motors, plug-in hybrid and pure electric versions of the A-Class and its derivatives are expected.