I'm not exactly sure which model that is, but you should be safe with standard velocity 22's. Do NOT use "Hi-Velocity", "Hi-Speed", or any of the hyper-velocity 22 ammo's(Stinger, Mini-Mag, etc, etc).
Much of today's .22LR is "Hi-Velocity" or with a similar moniker, so you'll need to look for stuff that isn't.
Blackpowder, 40gr or less bullet weight sub-sonic, and CB's are the safest ammo's to use until someone can verify the model and year of production.