Danny, if you go back to John's post #38 above, the enlarged view of the markings definitely looks like just under the '6 1/3' there are faint remnants of a 'C' and further on a '7'. I noticed this before but thought I might be hallucinating; now upon reflection I think not. In addition, that close-up changes my opinion on originality of the '6 1/3' mark, just a bit irregular in spacing and uniformity to be a factory job.

Don R.