We can narrow the date down on this one quite a bit.
Heat treatment on the cylinders began at 81287 as stated above, and this happened on September 2, 1919. Serial number 109161 came off the line on June 2, 1920; it was the first frame with the modified rear sight (square notch) and the flat top strap. I think that would tend to date production of your revolver sometime late in the year 1919. (Source: Neal & Jinks, Revised Edition.) Of course, it could have shipped later, since S&W did not ship in serial order.
I agree with DWalt - $500 would be quite optimistic for this revolver.
Jack

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Jack
SWCA #2475, SWHF #318