Hi, and welcome to MTF!
Bush Hog is a brand name of a company that makes rotary mowers and other implements. They are still in business. They were so well known for their rotary mowers that their name has become the generic name for rotary mower. Almost everyone calls them "Bush Hogs" or "Brush Hogs" instead of "rotary mower", just like everyone says Kleenex instead of tissue.
The numbers on that metal tag look like a production date code and serial number:
87 9 probably means that it was made in the 9th week of 1987.
95000 looks like a serial number, but it might be something else. You can try contacting them to see if they can help you identify it more specifically.