I recall the cartridges that were kept with the revolver were wadcutter rounds that were seated nearly flush with the case mouth. Probably a mild load. I doubt that the revolver has had more than a few hundred rounds fired through it. It simply was not shot much. The action and barrel are in excellent condition.
Wadcutters would likely have been .38 Special, but as you said, mild.
Interesting thread on THR about this.
http://www.thehighroad.org/archive/index.php/t-567258.html