The 7-1/2" guns, if original, can command prices in the $800-$2000 range, depending, of course, on condition, condition and condition and presence of boxes, papers, etc.
It should have Ruger's varnished walnut grips and most likely a barrel rollmark without the Eagle image. There are, however, some of those BKH-47's that were made with the Eagle logo on the barrel. As others have suggested, verification by Ruger whether or not the gun was shipped with a 7-1/2" barrel or some other length is paramount. Shucks, some folks had their 10" barrels cut back to a shorter length! :shock:
Here's a side by side pic of a BKH-47 and a BKH-46 from Flatgate's dungeon.......
flatgate