I came across a set of iron shafts that I forgot I had, but I need help identifying what their characteristics are.   They are Fenwick World

Class Flighted shafts (I know the company is no longer in business), but have no flex markings on them.  They are marked 5.0 on the shaft and the butt end has a sticker that says 263 CPM  My current set of Callaway irons are marked Regular Flex and 5.5  Does this mean that 5.0’s are Senior Flex?  Any help is appreciated…..