It is not necessarily old. I bleve they have a current model with fixed sights and a 3" barrel.
There are two or three versions of the lil SP101 with fixed sights and shorter barrels.
Yours does have the cool, wood insert grips instead of the more comfortable Hogue finger-grooved grips. I picked my 6" GP100 up with the big squishy grips a couple of years ago, so it is probably older than that. Of course, a kind forumite sold me some of the cool wood insert grips for dress occasions. They might be able to give you a year of origin: http://www.ruger.com/service/productHistory.html
I like the look of the shorty, but I don't want a carry revolver myself; I like them at the "range".