This idea is originally conceived for memorabilia with physical signatures. It might apply to other media as well.
1. Use OpenPGP to assign authors their unique PGP key fob. They sign serialized memorabilia (serial numbers could be assigned on the spot). In addition to the signature, a calculated
bar code is written to the item and the code is entered in a database (hand-held printer w/ PC).
2. The database is P2P. Copies can exist everywhere for free. On a frequent basis (daily) the databases update their contents by talking with the central server. The central server may give the updated contents directly or refer a database to a sibling database to offload bandwidth. The central server also collects database queries for billing.
3. Each database read or write requires a PGP key fob and is mappable to an individual with billing info. Pricing is TBD but say less than $1 per read or write.
On a read, the database would return the last recorded query and object info. Forging might be possible for a day or on one computer with a man-in-the-middle attack. However, making the same query from multiple computers and to multiple copies of the database should ensure trustworthiness. Maybe this type of multi-read would be billed at a slightly higher rate.
I think this system will work when the customer wants to know the real information. It wouldn't work well for copy protection.
The PGP key fob would be generated in the normal way. As a convenience/service to customers it could be put on a hardware key fob for a fee. Alternately a tech-savvy user could generate their own key fob for free. Updating the database with their key fob would require a billing address and some fee to prevent spamming.