They have mahle cylinders, not sure what pistons. The PO said JE, but unsure.

Often the manufacturer's marking is on the underside of the piston as part of the casting or forging.

I don't recognize the piston pictured, not OE though.

Jim

Is that a dome or a dish?

Mahle or KS is my first guess because the design on the left edge points to the flywheel, JE pistons don't have a piston pin offset. IIRC I think that flywheel mark is KS.
Also something to look for is JE pistons, or any forged piston, don't have full skirts.

NPR is also a possibility, they made T4 pistons back in the 80's, but the engraving looks more modern.

If it has a shallow dish it's a 914 stock 94mm 2.0 piston, likely a late replacement set. Deep dish VW bus, flat top 914 Euro piston.
Dome NPR?