Beeman R1 - what pellets?

[Lobi]

Picked up a nice Beeman R1 in .25cal.
Like to use it for squirrels. I'm guessing the gun isn't going to be picky on what I feed it but wanted input. Brand, style, weight? Will it push light slugs?
Also, any way to date it? No Beeman logo on the checkered stock so I'm guessing early gun?
Thanks

 

[A.G.R]

.20 grain H&N ftt. 25.3 are to heavy for short stroked R1

 

[Lewis]

I'm sure there are ways to more accurately date it but the order of the address stamps on the action goes...

San Anselmo
San Rafael
Santa Rosa
Huntington Beach
Air Venturi

Which stamping does it show?

 

[Lobi]

I'm sure there are ways to more accurately date it but the order of the address stamps on the action goes...

San Anselmo
San Rafael
Santa Rosa
Huntington Beach
Air Venturi

Which stamping does it show?

Santa Rosa