04072157
2004
BELT REPLACEMENT ON HUSTLER FASTrack
on the mower deck
It is the model number
Well, this link would be one, it is under Excel:
You could check with the Old Lawn Mower Club
Write down the serial number which should be printed on a serial number tag somewhere on the mower. Take the number to your local John Deere dealer and they should be able to tell you what year your mower was produced.
606
I believe it a engine on the back with valves
To determine the age of a Kubota mower based on the serial number 20213, you would typically need to refer to Kubota's production records or a specific model's serial number guide. Serial numbers often indicate the year of manufacture or the production sequence. If you have access to Kubota's resources or customer service, they can provide more precise information regarding the age of that specific mower.
That would depend on what sort/make/model of mower it was and what country it was made (and possibly sold) in.