No. Serial numbers aer NOT UNIQUE. They are intended to be unique to a given make and model- but a gun can be rebarreled to a different caliber.
By model, caliber and serial number.
The manufacturer is normally stamped on the firearm next to the model, caliber, and serial number.
Take it to a gunsmith
It is impossible to identify a weapon with just the serail number.
In most cases, if you give me only a serial number, and no info on make, model, caliber, then no. A serial number is not unque, or it would be 20 numbers long.
Without knowing the model and caliber, we can't tell. A serial number ALONE does not identify a gun.
Impossible to do with only the serial number. Provide a detailed description of all features, markings, caliber/gauge, barrel length, sights, etc..
Virtually impossible to determine caliber by just the serial number.
Unable to identify model from just the serial number. Need a detailed description of all markings, type of action, finish, caliber.
No way to identify maker by just the serial number and caliber.
Caliber can not be determined by serial number.
Can't tell the caliber from just the serial number.