www.925-1000.com

.925 clearly seen mark. C reverse E mark similar to European CE. Unidentified nib marks. Star and 5 digit sequence.....may be 40510 (viewed under 10X loupe). Do fancy pens qualify as jewelry?

Marks appear double struck...might be Italian maker 405 TO (for Torino).

Maker 545 TO appears to have worked on a Borghini sterling ballpoint in 2012 ( from a commercial listed view).

This has a list of several Italian registration numbers and the Pen maker brand associated with them: http://www.fountainpennetwork.com/forum ... d-italian/
Scroll down a few entries.