The pen had been inked, and when I tried to flush the barrel I kept getting blue ink coming out of the barrel, long after it should have come clean. Figuring it was a thich layer of dried ink, I ran a cotton swab into the barrel, only to find some sort of sponge seems to have been attached to the inside of the barrel, completely at the end.
The sponge (or spongey material) is securely attached to the end of the barrel and does not easily come out.
Has anyone who has one of these seen this configuration before? Was this some sort of ink-maker system where the sponge was loaded with a dry or concentrated ink, so you could just add water? It certainly is making this pen difficult to flush or change ink color.
Yes, there is a sponge/foam plug inserted into the barrel in each NSF pen that I have seen. I think the purpose of this is to restrict the ink capacity to prevent the typical ED overflow at low ink levels.
The sponge can be pullled out using long foreceps.
The white section insert can be similary pulled out to enable the use of a converter or carts. In fact, the sponge plug will need to be removed in order for the converter to fit into the barrel.