Yesterday I posted some detailed information about patent coverage in Scirus. Here is a more detailed breakdown for U.S. patent coverage:
Utility patents, 1790s-
Reissue patents, 1870s-
Design patents, 1976-
Plant patents, 1976-
Defensive publications, not included
Statutory invention registrations, 1985-
Additional improvement patents, not included
Defensive publications and additional improvement patents appear not to be included at all. Additional improvement patents were allowed from 1836 to 1861. Only about 320 issued. The USPTO registered 4,488 defensive publications from 1968 through 1988. DPs are published abstracts of unexamined patent applications. The entire file of a DP, including a copy of the application as filed, may purchased from the USPTO. DPs were superseded by statutory invention registrations (SIRs) in 1985. Both additional improvement patents and defensive publications are available in the USPTO patent database.
Scirus covers plant and design patents from 1976 forward. Design patents were first registered in 1842 and plant patents in 1931.
You can retrieve a specific US patent by searching the number as a keyword using the following formats: