SCSW dates it around 1938-1939 from the serial number, 1154XX.
Keep in mind that serial numbers can only really be used to get a rough approximation of when a particular gun came off the assembly line and the only thing that is really traceable is the shipping date.
Now, with the .32-20 HE, we can be pretty certain that there was no production after about 1932. Yes, they remained in the catalog until 1940, but they were pulling them from the vault; they were not assembling them for the last 7 or 8 years they were listed. We have evidence of .32-20 HE revolvers with serial numbers over 140000 shipping in the first half of the 1930s.
I would tend to agree that one with a serial number in the 115000 range shipped in the early to mid 1920s. But only a letter will tell you for sure.
The mystery to me is the caliber marking on the six-inch barrel it is simply "32-20 CTG." According to SCSW it should be 32 W.C.F. CTG.
What this barrel legend most likely tells you is that your revolver shipped after 1922. The 32-20 HE revolvers carried three different barrel legends during the years of production:
From 1899 until 1914, it said, 32 Winchester CTG.
From 1914 until 1922, it said, 32 W.C.F. CTG
From about 1922-23 until the end of production, it said, 32-20 CTG.
Of course there are overlaps because of leftover parts, but the legend 32-20 CTG did not appear until late 1922 or early 1923.
Jack