I haven’t come across this particular ferrule design before. The male section shown above has an outer sleeve at the left hand end of ferrule, into which the female ferrule has to be inserted, thus increasing the strength of this joint. However, any damage to this outer sleeve means that the joint can’t be completely inserted. That probably explains why we don’t see this design now. This example can be seen on Foster’s “ Perfection” and possibly other Foster rods.
This made me wonder how many other weird and wonderful designs for ferrule fittings were made for vintage rods. I have a few examples in my collection, but I’d be interested to see examples from other TFF members.