The Diamond was not quite the first pen offered by TWSBI, but it was the first that came from their policy of mass consultation. After a sampling of the rather diverse opinions to be had on the Fountain Pen Network, the pen appeared as a relatively large piston filler in a relatively indestructible polycarbonate body, with a relatively astonishing mass-market price. The early adopters of the pen raved about it, leading to a certain amount of controversy; the fact that it was of a similar size to a rather expensive German pen and praised for the good quality/cost ratio led a bit of a backlash from those who could not believe it was as good as a one which cost ten times as much, which is not what was being said in the first place.
The TWSBI Diamond is, however, a startlingly good pen. The initial run proved to have some problems with the piston seal, which later versions avoided and for which replacements were sent out (whatever else one may say about TWSBI, the customer service is excellent). This handing out of replacement parts was a sufficient response, as the Diamond is meant to be extremely user-serviceable; the box in which it is sold includes a wrench for extracting the filler mechanism, a small but sufficient supply of silicone lubricant for the seal, and a detailed instruction sheet. It is not merely the opinion of some pen-fanciers that this is a good thing, either, as it has garnered a couple of design awards. The Golden Pin is apparently a thing instituted in Taiwan (whence TWSBI) simply to pat upon the back any product their Ministry of Economic Affairs thinks is cool, but the Reddot is an actual big international deal, which has also been given out to heavy hitters like Apple.
The first release of the Diamond was the 530, which as far as anyone can tell is an entirely arbitrary number. In 2011, it was replaced in production by the 540, which in addition to having benefitted from the real-world trials of the piston seals has a somewhat less grabby seal at the interface of cap and barrel; there were also some users who found cracking issues with their 530s, which was traced to a problem in the way the specific materials cured over a period of months; these pens were rather harder than the 540, but that hardness brought with it brittleness. Another variant, the 550, is projected for the near-future; it is to have decoratively anodized aluminum components to its filler. There are also a metal-bodied version (850) in the works. The replacement of the 540, the 580, is a further effort to address the question of cracking, with more metal at the ends. The mechanism remains consistent from the 540.
The seals of the cap are apparently meant to keep the pen from experiencing any unease while being carried aboard an aircraft, and from all reports works quite well. They also serve to keep ink fresh and usable in the pen for remarkable periods; I have left one sit a month between uses and found it still willing, and that same test pen bore a single load of ink for nearly five months without any evident thickening. I don’t recommend this kind of abuse, but it is nice to know a pen can hold a charge.
One of the few more or less valid complaints about the Diamond line is that there are no solid colours. While there have been many different colours introduced, every example offered for sale to date has been transparent. This is not a terrible deficiency, of course, and it definitely allows for a sound idea of how much ink remains in the pen, but there are some folks for whom a transparent pen is simply unappealing.
Where the Diamonds have mainly garnered praise is in their functionality. The points, which are at the moment made for TWSBI by German suppliers, are quite supple for steel, and will allow a little bit of line variation. Plans are apparently afoot to bring point-making into TWSBI’s own hands, and I hope that this won’t affect this remarkable feel in writing. I’ll also mention that the points are easily interchanged, and there is a rather clever ink-bottle offered by the company which makes for about as mess-free a pen-filling as one gets with a Snorkel.
In late 2012, TWSBI introduced what their website describes as the Diamond Mini. Since that pen does not itself have the word “Diamond” on it, I’ve put it on a separate page.
Production Run: 2010 – present. The 540 ousted the 530 from production in August, 2011, and was supplanted by the 580 in March 2013
Cost When New: $50.00. The 530 cost slightly less, due primarily to a less complicated distribution chain, but in being less complicated it also threw more work onto the desk of TWSBI’s management. In fall of 2012, the cost of the 540 dropped to $40.00 (rumour then suggesting an imminent release of an improved model), although a special “ROC100” edition stood at $55.00.
Size: 14.1 cm long capped, 17.4 cm posted, 12.9cm uncapped.
Filler: Piston, capacity approx. 1.2 ml in the 530, 1.5 ml in the 540. The maker rates the 540 as carrying 1.95 ml, but this represents the entire volume of the ink chamber; one has to struggle to abolish the air bubble as mentioned in the last paragraph of my discussion on piston fillers, which can be messy. It might be less so using one of their own clever bottles; I’ve not had a chance to try one out yet.
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.