That is a well used example of an uncommon 4" 32 1st Issue. Does it have a serial number above 10,000. I do not have one and you do not often find them.
Problem is that this model has never gained much collector interest and values remain low, plus ammunition cannot be found for them. I do not think there is any documentation detailing how many 4" guns were made, so whether they are uncommon, scarce, or rare may never be determined.
The SCSW4 does state under Variations, "est. 200 made in 4"." The one I have has a ship date of Apr 10, 1866, one of a shipment of 10. (another member in formed me of that, perhaps the former owner of your gun). The s/n of my gun is 19391.
I believe condition has as much to do as rarity in pricing these.