martin, i wen't up to grass valley with the model T club (stock Ts) 3 years ago. we visited both the musium/machine shop and the mine and owners house. did you by chance visit the mine? there was a BIG lot with all sorts of mine machinery/equipment, each one had a plaque telling the history and function of each piece. it was VERY COOL. there were also several large outbuildings for equipment repair and a large blacksmith shop. how do i know it's the same place? i have a mounting core drilling sample sitting here at my desk that says "empire mine state historic park
grass valley, ca"