Well, I couldn't resist any more and got a Sentinel, even though I still haven't decided what I'm going to use it for. Advice: if you're thinking of buying one, you should do it soon, because it's not a commercial product, they're not being produced anymore and once the stock is sold out, it's gone. If you don't mind a knock-off, the original post above has where you can find one on eBay.
It came in this messy packaging. Inside was this simple telescopic square plastic tube.
It's wonderfully smooth and solid. Surprisingly heavy, though.
The cap actually secures in between 2 to 2.5 turns, which makes it very fast to open and close.
This is the cap inside the barrel:
- Firstly, the whole cache is 6" long but the usable space inside is barely 3". From the technical diagram the length inside should be 3.742", but the caps are so thick, the usable space is only about 2×1.375". I can't even fit in a normal plaster without sticking part of it into a cap.
- The caps' walls are very thick. From the picture of the cap inside the barrel, you can see it narrows the usable diameter considerably.
- Like I said, it's heavier than expected, and I noticed the weight comes mainly from the caps. The barrel itself is actually quite light.
- The design seems to have prioritised strength over portability, but I think there's no point making the caps that much thicker than the barrel wall.
- I bought this because the dual-ended design meant things wouldn't get stuck inside, but the caps are so deep and narrow that things can still get stuck in them. They're actually deeper than my aluminium capsule below.
It's really sad that hardly any of the Singapore coins fit in it, much less so the Australian coins. I used it as a first-aid kit at first, but like I said even plasters don't fit easily, so I switched to an M&M's tube.
- The streamlined outside - almost the whole tube is the same diameter as the barrel. It can be used as a rolling pin. Although this means the caps fit inside and take up space.
- Square threads!
- The dimple in the bottom cap allows it to stand.
If I were to redesign this, I would:
- Make the cap walls thinner - no more than half as thick.
- Make the caps shorter - no longer than the current length of the bottom cap
- Make the threads shorter, if possible. Maybe make them thinner. Double start.
- Have less "stages" in the hollowed out caps. Maybe just one section. No point making so many sections if they're going to be narrow and have things stuck in them.
- Flatten the top and bottom so it can stand on either end.
So, really solid and secure, but I think the design could have been more space-optimised.