I collect used and unused as separate collection (That's why German 7350 caps, 3918 are used and ~3400 are unused). A lot of collectors are of opinion that a lot of them are doubles. I collect different factory signs if the caps are different (size, color, ...).
Every cap is filed in my database with picture. Jan 20 2009: now you can also search in my database (advanced search probably next months)
La Trappe Koningshoeven, Herforder series, Urthel, Maddballs and many others