A few years ago I built a database that included 'stamp issuing entities' along with dates and the evolutionary relationships between them. It turned into a massive project which I eventually gave up on after pouring a lot of hours into it; I recall thinking that it would be a life long project that would never really be finished.
If you still have this, I'd love to see the design info. "Issuing entity" is something I've been trying to define for myself as I begin to design a database for keeping track of my collection. It would be interesting to see where you were taking just this one part.
And if I'm overstepping, please accept my apologies. I was a DBA for a time, but get more DB use/development time in my current role as a developer.