they tell you quite a bit about the Mule you have
It will warn you if it is a Magnesium Mule
It will tell you oils to use
It will tell you who built it, when it was delivered
what type and model your mule is.
they are full of information, if you need there are people making
new data plates with your information added to them.
http://www.militarymules.com/main.html
If not carefully clean yours and do not paint over them, you need to be able to tell
what yours was originally. This is one of mine.
We can see it is a Baifield Mule, M274 A5 (aluminum)
that was delivered in 2-69, that information alone will get you started
if you find you need to know more about your mule.
What it will not tell you is what has been done to it since.
For instance my mule has a 4 wheel steer kit installed, this was not
standard on the A5 models.