Need to know if its a 5 or 6 shot, is the hammer exposed or internal, aluminium or steel frame, any model markings stamped on the frame under the cylinder yoke.
I'm going to guess its a steel 6 shot with no model markings and an exposed hammer.
This would make it a .38 Military & Police Model of 1905 4th Change manufactured between 1920 & 1927. If this is the case it has a heat treated cylinder (introduced in 1920), but the quality of the steel is not up to modern standards so shooting of PlusP or +P+ ammo through it is not recommended. It also lacks the positive internal hammer block safety introduced in 1944. If dropped the gun could fire, so leaving the chamber under the hammer empty is the prudent thing to do.
In excellent condition the gun would be worth around $350.
If its a 5 shot get back to us with the details requested above for a different answer.