PenBBS production is basically what you get when a quantity of pen enthusiasts stir their ideas into a single bubbling caldron. It is therefore unsurprising that the 500 is roughly what you would get if a TWSBI Go managed to get over the fence of a yard where a prize Conid Bulk Filler was being kept; it has some of the best elements of both of those pens.
The function of the filler is pretty much just the same as the Go’s– a stick-piston fitted with a return spring, allowing a complete fill on a single working. Where my comparison to a Conid comes in is the specifics of how that single working happens.
Unlike the TWSBI, the works of the 500 are permanently fixed inside the barrel. The back of the piston has a threaded hole in it, into which a rod fits. The rod is threaded at both ends, and when the pen is in use, it rides inside the piston. At filling time, it gets unscrewed and drawn mostly out of its hiding place. The interior set of threads gets mated to the piston, and you now have a long-throw actuator.
I find this form of the mechanism substantially more elegant that the Go, where I first encountered it. You only have to remove the cap to fill the 500, rather than both cap and the barrel, which means few things rolling around and distracting you when there’s an open bottle of ink about. You can also grip the barrel well toward the back during the fill, reducing the risk of rubbing fingers against the ink-laden mouth of the bottle.
While I am favourably impressed with this pen, I do have a couple of small quibbles. Despite the end of the barrel having a step in, giving the visual impression of a false blind cap, it is not a good pen for posting– the end of the barrel may be narrowed than the front, but most of that narrow bit is still wider than the inside of the cap.
I also worry slightly about the eventual fate of the trim ring at the back of the section. It will be exposed to ink of various pH levels, and I know from experience that my own skin oils can give some chromed pot-metals serious problems.
I have not tried to dismantle the filler (yet– I suspect it’s a fairly simple matter of using grippy material on the tail disc), and for basic lubrication refreshment I would think the easiest thing to do is unscrew the section and work through the hole this opens.
The writing performance is good, or at least good enough; the steel point is smooth and has a very little bit of spring to it.
Production Run: Introduced in 2020. In current production, although PenBBS is somewhat intermittent.
Cost When New: 598元 according to the box, but bought from the maker’s Etsy page in January 2020 for $35.99. Either I’m misreading the box, or people in China are paying a steep premium for this pen.
Size: 14.5 cm long capped, 18.7 cm posted (but don’t), 13.5 cm uncapped.
Filler: Piston, capacity approx. 1.4 ml.
If you are relying on the preceding information to win a bet or impress a teacher, you should read the site’s scholarly caveat. Remember, this is the internet, and it’s full of bad information.