How about taking that left grip off and taking a picture of the frame. That serial number gives information needed to determine date of manufacture. A picture of the spring will tell if it is black powder only or not!
Topbreaks (Safety Hammer) .38 cal. S&W large frame
Owl is looking to the barrel, cylinder is free wheeling when at rest, for black powder cartridges
Model 1, First Model or Old Model
Single top latch, 100'000 were produced in 1894, serial number without letter prefix, marked on the top of the barrel rib
IVER JOHNSON'S ARMS & CYCLE WORKS FITCHBURG. MASS.U.S.A.
PAT'D.APR.6.86.FEB.15.87.MAY 10.87.DEC.26.93 PAT'S PENDING
Your revolver is a 1st Model second variation that was made in 1894 and is chambered in .38S&W
1st Models without the side pin cylinder retainer and very early 2nd Models had the serial number on the bottom of the butt strap so that's normal.
As has been noted it was designed for black powder loads only! Personally 1st Model .38's are about the only ones in my collection I'm hesitant to shoot. They were only in production for about 2 1/2 years when Iver Johnson figured that the barrel latch wore out too easily on the .38's and switched to the 2nd Model with the familiar twin post "T" latch.
Yours with the release lever falling out I would keep in the "wall hanger" category.