NY Times: Numbering the "X-Patents"

Officially, U.S. Patent No. 1 was issued in 1837. But according to an August 9, 2004 article in the New York Times, at least 10,000 U.S. patents were issued before July 1836, when every one of them burned in a fire. As the lost patents were recovered they were assigned sequential numbers starting with 1, and an "X" was added to distinguish them from the post-1836 patents. In fact, some were recovered out of order. When that happened, the recovered patent was given a fraction number, like Patent 127.5X, in order to keep the patents in the proper sequence. In the 168 years since the fire, only about 2,800 have been recovered.