I have two blue 15-2's, one is a 4" the other is a 2". Blue 15's in fantastic condition are basically "A dime a dozen" because many departments issued them! Nickle post war K frames were produced at a minor fraction of their blue counterparts.
But DON'T LET SEMANTICS FOOL YOU! It can only be a collector gun if it is in a collection. The minimum number of guns in any collection is ONE!
Collector grade, Collector Gun and Collection are all matters of the owner's attitudes or intentions. You alone decide that term for your possessions.
The value of any object, is the amount that you actually buy or sell an item for, not what it might be worth, not "These sell for $X on the internet, and not "I paid $X for one like it."
All that being said, your gun looks worthy of any collection. It also looks "Safe to shoot"! But don't let any one else's opinion dissuade you, Do with it as you and only you see fit!
Ivan
PS, It is safe to shoot +P's in it!
EDITED TO ADD: If you needed a hammer and went to a store and bought a hammer (that thousands like it were made) that sat on the shelf unsold for 38 years, got it home and someone suggested that it was "To Collectable to use!", you would laugh them out of your workshop. ANY FIREARM is a tool first and a work of art way down the road. "Collectable" is a recent invention, to separate you from added amounts of money! All that being said, I too have accumulated and collected a few hundred guns, They were all made with the intent of usage. A few however, have been Honorable Retired.