Odd combination, the frame appears to be from the early 80's due to fork crown, brake fixation set-up and drop-outs that you described; so it is odd that the pre-CPSC components would pre-date the frame by a number of years. I suppose that given it comes from a small builder, it could simply be because their sales were so limited they may have only bought in components on an irregular basis. It can also be that the owner of the frame simply transposed parts from an earlier bike over to this frame.