information from the seiko casing database is partly available online:http://www.boley.de
click tab - EASY REFERENZ and a Seiko window appears enter the case number or nothing for all cases.
I think there's about 30000 casings overthere, I was happy to find some info unavailable in my '77 csing guide.Unfortunately no 4006 calibres somehow....
Site is in German, but you will probable get the meaning.
Just in case:
Glas = Crystal
Krone = Crown
Bodendichtung = Case gasket
Glasdichtung = Crystal gasket
thanks to Dave (7s26b) for the tip!