I finally decided to organize my unmounted on the storage sheets by theme, and to create index sheets for reference organized by manufacturer. :) I haven't decided whether or not I want to keep my mounted stamps mounted or unmount them. I really love seeing all the stamps lined up in the bookcase, but I don't have enough room for them all. I probably will just unmount the ones I don't use very often since that will free up more space.
Jeannette