I finally succeeded in getting this inherited Duofold to work, decades after it came into my possession! I know a lot more now and had decided to give it another go now that I realize some pens don't twist to fill. This had been my grandfather's and did not come with a box nor instructions. I filled it with a lubricated ink (Monteverde) and it seems to have worked. Time will tell. I can't tell what size nib this is, but it seems to put down a fairly fine line. I'm pleased as punch!