I got to thinking about the vintage of the threaded taper crimp die, so I went back to do a little "Price List" research. I have price lists from 1945, 1958, 1960, 1966, 1968, 1973, 1978, 1979, 1981, 1983, 1988, 1990, 1991 and 1993. The price lists prior to 1978 list part #18 Crimping Die, but do not list part #18T Taper Crimp Die. The price lists for 1978 and 1979 list Taper Crimp Dies for both the unthreaded 3/8" hole, and a 11/16-24 threaded hole. Price lists after 1979 only list #18T for a 11/16-24 threaded hole.
My price list collection has big gap between 1973 and 1978, so I can't say when Star started to offer an 11/16"-24 threaded taper crimp die, but I think it is safe to say that by 1978 they had converted to the threaded hole for the taper crimp die. Keep in mind that many old style tool heads have been drilled and tapped for 11/16"-24 taper crimp dies, so the existence of a threaded hole for the taper crimp die cannot be used to date the tool head much less the reloader.
Maybe some other members have price lists for 1974-1977 to help us better nail down the date for the transition.
I have never seen a Star tool head that did not have a hole of some sort for a taper crimp die, so I'm assuming that it was offered even though it was not listed on the earlier price lists.