Swing out the cylinder and look on the frame there for model marking. If present, we can begin there.

And a full photo of the gun in reasonable size will tell us much, even if the gun was too early (pre-1958) to have an assigned model number. The exact shape of the cylinder release, for instance, says much. That has varied over the decades the gun has been made.

NOTE: Absalom was posting as I typed. I guess he nailed the date by serial no.

Don't fire a lot of Plus P, or you'll get premature cylinder endshake. Carry that ammo only when you may need the added power. Plus P and .357 Magnum ammo is not for routine range use. It 's for killing. (I know your gun isn't a .357, but threw that in for those reading this who do own .357's.)

DO NOT fire Plus P Plus. Don't have time to say why,but don't. It wasn't meant for .38 guns, really, but for use in .357's.