A question for the modern Waterman experts: I own the L'Etalon and several Phileases and have several Waterman twist-type converters. Re: the end-point of the converter that is inserted into the section: some of my converters are threaded (like a very fine screw), at the metal part that is just above the black plastic "nipple" that covers the piercing post. And on other converters, that same metal part (at the end that is inserted into the section) is not threaded but rather is smooth.
Question: Why are there 2 types of Waterman twist converters like this? Looking into the section itself with a medical instrument, I can see that neither the Phileas nor the L'Etalon is threaded around the piercing post.
Seems to me a threaded converter being inserted into a non-threaded section is not a good idea. I bought all these converters from various places I cannot now remember. Any help appreciated.