Serial numbers are usually on the left side of the barrel near the breech (loading port)
it was made in 1975
T427432 was made in 1982.
It would really help if you stated the model number. Also most older Benjamin serial numbers began with a "B" or "H" or "T".
Unfortunately I can't tell you the age by the serial number. State the model number, that will help identify it's age.
What condition is it in. That determines the value.
It was made in 1969.
You have listed the model number of your rifle,not the serial number.
Most likely around late 1956 according to Crosman who owns Benjamin.
By the serial number on the rifle.
The numbers .308 are the caliber of your rifle,not the model number.Please include the model number and serial number to get the age of your Winchester rifle.
The model 340 was made between 1969-1986. I believe you have the first number wrong. I think the Serial number is T280984. If so it was made in 1977. See the link below for Benjamin dates. Crosman owns Benjamin and Sheridan air guns
Benjamin made several different rifles. Please state the model number (It's most likely on the barrel) and the condition of the rifle to get an estimate of value. Is it still working? Is it in Excellent, Very good, Good, Fair or Poor condition? Unfortunately the serial number doesn't help, I need the model number