There are a lot of "white brand" pistons for Rexroth A6VM motors on the market. All look nice and finished, however the quality varies a lot, and in the worst case scenario such pistons can end up looking like this after but a couple of hours of "hard work".
Here are three tell signs to determine if a piston in your A6VM motor has "oriental roots":
Piston rings. Non-original pistons usually bring along low quality rings, which can be easily identified by the crooked gap.
Lubrication hole in the center of the piston. In a non-original piston the hole is not centered - which is the direct result of the simplified machining process. Original Rexroth pistons have a hole that is perfectly aligned with the piston centerline.