It was made in 1978
It was made in 1974
it was made in 1975
Yes
It was made in 1978. Today Crosman owns the Benjamin line of air guns.
Serial numbers are usually on the left side of the barrel near the breech (loading port)
Unfortunately I can't tell you the age by the serial number. State the model number, that will help identify it's age.
T427432 was made in 1982.
Serial numbers are usually on the left side of the barrel near the breech (loading port)
It was made in 1969.
What condition is it in. That determines the value.
Most likely around late 1956 according to Crosman who owns Benjamin.