It is also possible that this brochure, along with the cancelled stamp, was sent as a 'gift' to a subscriber who has been putting in orders for a peroid of time??
Canada Post once sent their customers something similar with one of the train stamps on it as a 'complimentary gift'. I believe this was in the mid 1980s. Also, the UN Postal Administration has done this in the past as well.
Chimo
Bujutsu