Re: COLT D.A. 38 ?
Colt's early swing-out cylinder revolvers had a variety of problems, so the design was changed often in the first few years of production.
The power of Colt's name at the time was enough to gain public acceptance anyway, and even the US Army adopted the design while it was still in the process of evolution.
Your gun does have cylinder locking notches, for instance - they are just in the rear face of the cylinder, along with the cylinder ratchet. This was a dubious feature carried over from Colt's earlier double action revolvers.
The history of these guns is quite involved, and I don't know it off the top of my head. Colts are so popular that there are certain to be books that have the whole story, and people here who either know it or know what the books are. Welcome to the Forum!
BTW, those same people would probably like to see pictures of your gun, and would be able to tell you more about it from them.