Casual researchers will find the free patent databases easy to use, and more experienced researchers should not be dissuaded from searching the commercial databases or patent libraries themselves. The very large commercial databases, like Inpadoc, are particularly easy to use. Of course, there are occasions when patent searches are critical, and experts should be sought. Certainly legal assistance is required if you are preparing to lodge your own patent but patent data as a source of information is another matter. All patents are given a special number.
Australian patents have an alphanumeral which includes the year.
Canadian patents are numbered. US Patent Classification is similar in many ways. Work on IPC 7th Edition is well advanced. The system is highly specific and logical, and includes numerous cross-references to other codes of similar form or function. Think of this as the Dewey Decimal System for patents.