This format can be a patent application number, but the number of digits is wrong and missing. Please confirm the digits. Then, the digital form of the patent application number before 2003 (8 digits plus a decimal point), such as 8820 1465. X, still the one in the picture.
You can also see the details of that patent. I don't have a good internet speed here. You can find this number on the left side of this website: /zlsqzn/sqq/