I think the only way to really know is to auction it and see what it brings in to ruger collectors. I have a ruger "made in the 200th year" security six in 357mag that was never in the catalog it was only made for the 200th year run. I still have the orginal box and paperwork. The model number is "GF32" if i remember correctly its a security six in stainless, 357mag and a 2 3/4" barrel with fixed sights. My point is did you check on your model number on being correct with the production run or is it like mine 357 is too for 1976? I was just wondering if they did all of the 1976 200th year models like mine. I have a few others from 1976 and i'll have to checkout the model numbers too i just thought of it now and i'm not sure. That could mean its worth a little more.