Daisy never made a model 120 pellet gun. Are you sure you don't mean a 120 Pellet rifle?
If this is what you are asking about then restate your question with additional information, such as the current condition of the rifle. Give it a ration like Poor, Fair, good, very good or excellent condition. Also stat if it is working or not. Then I will be able to give you an estimate of value.
Daisy made a model 120 pellet rifle from 1984-85. It was made of by El Gamo of Spain.
This is not a BB gun, but it is a Pellet rifle made between 1984-85
The Crosman 120 is a rifle not a gun. It is a break barrel. Cock the barrel all the way down and load a pellet into the rear of the barrel. Pull the barrel back up and it' is ready to fire.
The Daisy model 120 air rifle shoots at 500.fps.
It all depends on the current condition. You did not state the condition so no estimate of value can be given.
It was made between 1984-85. El Gamo made it for Daisy.
Which Model? anywhere from $40 to $120
The Crosman model 120 was made between 1952-1954. The has a fore arm pump and shot a .22 caliber pellet not a .177 common pellet. The .22 caliber pellet was loaded through the loading port at the rear of the barrel. .22 caliber pellets are still available through most sporting good stores. Actually it's a very nice rifle.
$650
The Winchester ranger model 120 is selling for between 90-180 dollars at this time.
about £120
50-120 usd