The Slabside is a KMK678GC
I only know this because I had one of them I bought in 1999 & sold to a good buddy who still has it..
The first K = Stainless & 678 = 6 7/8" & G = Government Target Model
The C = Competition Target Model or Slabside
The Blue book of gun values doesn't always show every variant of gun made
Ruger makes several different variants of each were barrel lenth etc are changed..
Congrats on the Stainless Government Target, There great shooters, I wish I would have picked up the used one I saw Jan 1st for $350..
Hope this Helps..
Are you planning on selling it or just wondering it's value??
You won't have any problem selling it if you want to..
Not really rare but sought after never the less..
Gary, Thanks for all your help. I don't plan on selling it right now. Again, You've been very helpful, Mike