Yah, I am pretty sure Fred worked in the magnesium casting department, right?
To be serious, the custom bow orders that were available in the early to mid '70's is something that I think not many people know much about. In the catalogs it says custom orders are supervised by Fred or Owen Jeffery.
I would think this is possibly authentic or maybe not, I have only seen a couple bows with that phrsae on it, however, they had some sort of custom handy work, I am not sure what is custom about this bow.