Small Engines (Lawn Mowers, etc.): age of a craftsman engine

Question
I have an OLD Craftsman engine, model 143-651052, serial number 50280, that I wish to know the age of. I received help from your web site in the form of an original owners' manual which GENERALLY explained the Tecumseh system of assigning serial numbers. That was SOME help - as far as it went - yet still did not pinpoint the age of the engine, and here's why. As you know, the first number in the serial number tells the year of manufacture - but it does not (as far as I can tell) tell the DECADE of manufacture. In this case the first digit is a "5"; fair enough, but would that be 1975, 1985, 1995, 2005, or what?? I'm sure you see the problem with this system... and what REALLY complicates things is that this engine has been sitting idle in my shop for at least 20 years.  So, as I said, I would just really like to pinpoint the exact age of the engine.  If you could help with this I would be so grateful.  Thanks again - Fred

Answer
Fred
The first two numbers are the mower's month of manufacture. The second two numbers indicate the day of manufacture and the third two will signify the year of manufacture.

Use this example to further determine the age of your mower: If the first six numbers are 031398, your mower was manufactured on March 13, 1998.

What you gave me was the mowers numbers not the engine but this should help you determine what age.