I knew we'd hear from you on this, Crutch! Tony LaPetri posted this photo on another thread. I recognized it, immediately, as a rare combination. I am wondering just how far inside of the tube the end of the #18 blade actually extends. I would venture to say not as far as a good many other examples featuring the Crutch tip, for the reasons you have mentioned.
This is just "me"...but it only makes sense that the longer the tang on the inside of this tube...the more problematic the Randall shop would have had in maintaining a perfectly round end to thread. Have you had a chance to see one like (or nearly like) this one, Joe? If not, I guess we just have to go to the MoMA and check this one out.
Thanks for posting, Crutch! Always good to get your educated spin on things....(well...maybe not "spin")
Best, Capt. Chris