I did some more research and found this. They could be 1997 tires based on this. Text from website in quotes.

"Here are the rules:

First locate the letters "DOT" on the sidewall of the tire. Nearby will be the DOT code. DOT codes are 10 to 12 digits long. BTW the digits can be numbers or letters.

The first 2 digits are a code for the manufacturing plant.

The next 2 digits are a code for the tire size.

The next 3 or 4 digits are a code for the type of tire.

The last 3 or 4 digits are the date code. The format is week/week/year/year or week/week/year. These are always numbers.

Starting in the year 2000, the date coding used was 4 digits. That means the largest number you should see for the year code is 09. Before 1999 the format was 3 digits. 1999 and 2000 are transition years, so you will find both 3 and 4 digits.

The date code only has to be on one side – and it is permissible for there to be a partial DOT code, so long as one side has the complete code."


The tire manufacturing (plant) codes are found here:

http://www.harriger.com/tire8.htm

It appears that Hercules does not actually have any plants with their name on them. Your tires were manufactured by Cooper Tire and Rubber, Findlay, OH based on the above. Joe