I've not found anything in the spools so far, but I did have the idea
of putting notes inside about where and when I bought the roll, with
room on the note for others to write their name and date.  It would
be nice to find a note like that that somebody wrote in 1910..., but
I will probably ever find one.

But not all rolls support this secret storing room.  I have many Hupfeld
rolls and they have solid wooden spools.

Greetings from the Netherlands,
Niels Berkers