A H&R six shot .38 is the "large frame" that waidmann mentions.
I assume it is a top break, the solid frame guns of the era are considerably less valuable.
One in good shooting condition as you describe is worth a bit to a Cowboy shooter for pocket pistol side matches, but still only a bit. Maybe $100-$150 in tip top but not as new condition.
You have to bear in mind that these were inexpensive guns in their day.
A top break H&R cost less than half the price of a Smith & Wesson, a solid frame was less than a quarter the selling price. Like $7.50 in 1939.
Sorry, I cannot date it, these little guns were made from the 1880s until the eve of WW II, and to some extent after.