Ithaca Firearms manufactured the Lefever Nitro Special shotgun with serial numbers between 101600 and 119899 in 1922.
In order to determine the age of Lefever shotgun, the serial number must be known. However, Lefever shotguns were only made and distributed between 1885-1916.
I would say that with the serial number 1321XX,we are looking at your shotgun being made by ithaca(who made the lefever nitro special) in 1924.
You need the services of an appraiser
The Lefever was mfg. in 1935.
The model number is on the water table directly after the serial number, usually a letter ranging from A thru I with I the least fancy.
Examine with high power magnification.
If it is a double, remove barrel and you will see it along with serial #.
Turn of the century.
In 1916, Lefever Arms Company was sold to Ithaca, who continued to make guns under the Lefever brand. Your serial number would date to around 1935-1937.