Lot
2104 
1851, 1¢ blue, type II, tied by "Philadelphia, Pa." cds paying the drop letter rate on sealed Knight's Safety Patent envelope addressed to the creator of the envelope, envelope sealed and fastened with clamped eyelet at top through upper portion of stamp, with additional similar addressed cover (without franking) opened to show printed Knight's Improved Safety Envelopes advertisement with illustrated instructions on it's use, Extremely Fine. Scott No. 7 Estimate $7,500 - 10,000.
IN OUR OPINION THIS IS THE FINEST UNITED STATES PATENT ENVELOPE IN EXISTENCE, WHICH WE SOLD IN OUR WASHINGTON 2006 SALE FOR $14,000 HAMMER.
In 1856, Robert T. Knight patented his Safety Envelope which retained the main features of the old folded letter and added an additional clamping feature. This was designed not only to prevent tampering with the envelope, but after opening it held both enclosure and envelope together for filing. A group of these letters then could be bound together like a book for storage. Like the Leeds and Franklin patent envelopes, this idea never caught the imagination of the public.