The so far unidentified mark below was seen on a most likely early 18th c Dutch shell guard sword as shown in this video where the criminally undersubscribed current owner takes it apart. He gives a more detailed description of the sword here. The blade also has VOC marks, Z (for Zeeland) and M (for Middelburg), and "1717" (presumably a date). Possibly also a D on the shoulder of the blade. The pommel side is on the bottom of the image.

I looked through Kinman's "European makers of edged weapons, their marks" and Lenkiewicz' "1000 Marks of European Blademakers" and this thread, but I did not find any exact matches.

Does it ring any bells?