In 1991, another imperf souvenir sheet was issued. This time, instead of being a free gift to subscribers, the souvenir sheet was sold in order to raise money for The Postal and Philatelic Museum. Subscribers were able to buy both Mint and FD cancelled souvenir sheets through the philatelic service. As you can see, the imperf souvenir sheets are also individually numbered. I don't recall if there were any limits to the number of souvenir sheets you could order, but there was a hefty premium on the sheets over the normal perforated variety. Once again, there are no spots in the majority of albums for this issue.