About 8 years ago when I was on the hunt for Lava treatment rOtring writing instruments, I happened upon a fellow writing instrument enthusiast who had managed to obtain some vintage rOtring pens. He wasn’t a serious collector, so he basically began selling off a good portion of his rOtring cache. As luck would have it, he had 4 capped rollerball pens (600 Newton model) that featured the Lava treatment. There was just one caveat–the front tip was non-standard. The opening was wider (possibly double the size) than a normal Newton 600 that’s compatible with the G2 refill type. By the time I’d gotten to negotiating with him on these, he’d sold two of them, so I grabbed the other two. A couple of years later, I sold off one of them on eBay. Now, a G2 refill will still work in this, and it’s fairly tight enough that there’s not much tip drift, as long as you don’t press down too hard. You can of course fill the gap with either aluminum tape or some DIY fashioned plastic collar.
Still, this left me curious. Did rOtring have a special proprietary rollerball refill that fit this? Or was it meant to take something else as an insert, like a wide felt tip?