I've torn down engines with more miles than that and they didn't show any copper. Usually when the bearings hit copper it indicates a good bit of wear.
What I find odd with the picture is the number 1 and 5 bearings look good, which is mysterious to why. The number 1 main bearing is the furthest away from the oil pump and it's the last one to get any oil, yet it's not showing copper. Usually, the number 1 bearing is the first to show copper for that very reason. I think I would have the crank checked over, as when 1 and 5 bearings look good but the 3 center show copper, it indicates a problem.
If you plan to use the block and crank again I would check the clearances very carefully.