This is a Daisy Air Rifle known as the 25 chambered in BB, model 990025-603.
The Daisy Model 25 Pump Gun has been in the lineup for more than 100 years! It's a pump-action spring BB gun that pushes the .177 caliber BB at 350 feet per second" and features a blade and ramp metal front sight and flip-up peep or open read sight (adjustable for windage and elevation).
Features:
Caliber: .177 BB
Action: Pump
Powerplant: Spring
Velocity: 350 fps
