PATENT NUMBERS AND DATES

If you have ever had trouble dating old instruments, this list may be a help. It shows the first patent number issued in each year, so if you have a patent number, this easily yields the approximate date to begin with. If something is marked "Patent Pending" you can reasonably assume it was made within a year or two of the patent being issued. Remember that there could have been a year or more between the date of application and the final date of issue.