I didn't see your other thread, but it depends on the model. S&W topbreak guns in .38 were common in the 1920's, but they had also been making the M&P model since 1899, with the front cylinder lock added in 1902. That had a swingout cylinder, and you extract the fired cartridges by pushing back on the extractor rod. This is by far the most common system today, for all revolver makers. It is also the stronger design.
Are you a writer trying to determine what to say about this gun in a novel?
Keep in mind that topbreak guns, like the older S&W's and the Webleys do not auto eject the fired cases unless you smartly lower the barrel- cylinder assembly all the way. If you fired only a couple of shots and want to reload, just open the gun partially and pick out the fired cases.
Because either type gun was readily available in the 1920's, I'd choose the gun based on the character and the circumstances. What aura do you want the character with this gun to have?
Keep in mind that the topbreak ones also came in a hammerless version, with an internal hammer and a grip safety.
Did you watch the TV series, "The Lost World"? Remember that hammerless gun carried by Rachel Blakely as Marguerite? I think a real Marguerite would have chosen it because the hammer couldn't catch on anything if she fired the gun through a coat or a ladies hand muff.
In the two-part movie that opened the series, she did in fact kill a would-be assassin in London with the gun hidden in her muff.
But by the time she was on the expedition to the Amazonian jungle, I think she should have switched to the more powerful .38 Special swingout cylinder model. The topbreak guns use a shorter .38 cartridge of less power.
I think this answers your question, which I understood perfectly, being a writer, myself.
T-Star
P.S. Okay, I just found your other thread. You need to show us a photo, or tell us at least if the cylinder swings out to the left. Either type of gun might have been in TN in that day.
You are simply not giving enough information.