Magura changed the Marta pads around 2008 or 9, when they introduced the easy bleed port in the reservoir cover, if I remember correctly. Yours are the earlier type. I have at least 4 Magura original pairs from my old Martas in sealed packaging somewhere in the garage. Also, an Epic Brake Bleeding Solutions bleed kit, unused but open – I read the instructions.
£6/pair and £10 for the bleed kit, posted, if you’re interested.
Just to clarify, having now read the further posts, the round ones are the earlier, 5.1 type.