If it's T123136 it was made in 1972
T427432 was made in 1982.
serial number T170160 would have been made in 1973.
It was made from 1946 to 1985.
The model 132 was made from 1942 to 1986.
1980 see the link below. See the link for your date of manufacture
you need to state the model number not the serial number to get and estimate of value.
Around $50
It was made sometime between 1969-92.
Benjamin made this model from 1946 to 1985, but did not start serializing them until 1957. I also have a Benjamin Franklin that has no serial number. Before 1957 it is not possible to set an exact date. Just know it's OLD. The 137 is a .177 caliber pellet pistol the 132 is a .22 caliber pistol and the 130 is a BB pistol.
I think you answered your own question. It's a combination BB and pellet rifle. I can add this information. It was made between 1969-86. It a pump rifle using the forearm as a pump. The name Benjamin Franklin was a marketing gimmick. Ben Franklin had nothing to do with it. Walter Benjamin started the company in 1899 and today it's owned by Crosman Corp.
I suggest you go to Crosman.com and click on Support and ask your question there. Crosman owns the Benjamin line of air rifles
it was made in 1975