12-sided pound coins!

[drdoug]

The new 12-sided pound coin is in production, and will be introduced from March 2017. And it has 12 sides!

That means that when I said, back when it was announced in March 2014:I confidently predict that one result of this will be that the shape will change, so that it's constant-diameter, like the 50p and 20p pieces. Which I think in turn means

Comments

[steer]

I suspect that as the number of sides rises the problems of not being equal diameter diminish. As the number of sides rises in a regular polygon the deviation from being equal diameter diminishes. The slight outward bulge helps this even more.

[drdoug]

True, but the variation is still way more than you'd have as the tolerance if you were detecting the coin purely on diameter - from here, the max diameter is 23.5 mm, and the min is 22.7 mm - that's almost an entire mm, or 3.5% of the diameter. That's way more than you'd want to allow to exclude counterfeits.

Maybe. I'm trying to be less confident here, since I was wrong earlier. Um, that seems like a lot?

[steer]

Hmm... but detection on diameter... well, the pound coin is widely counterfeited. So I'm not sure detection on diameter cuts it as a security measure these days. Wikipedia says weight, size and magnetism.

http://www.gizmodo.co.uk/2014/03/what-is-the-new-1-coins-isis-security-system/

Apparently:
"However, to take advantage of the added layer of security iSIS brings, vending machines will have to be equipped with electro-magnetic signature detectors, and may require a refit to accommodate the new tech, and possibly even the new shape. How big a potential problem this is remains to be seen, though a public consultation ahead of any introduction into the currency circulation should ensure this is a seamless transition come 2017."

I wonder if they regret the iSIS name?

[drdoug]

Yeah, there's clearly something pretty clever about the EM signature of the new coins, and it's not just on the surface either. Presumably the basics must be relatively well known in the industry or it'd be pointless as a practical security feature. I tracked down a few industry forums talking about it, but they all assumed you already knew the basics and didn't say anything much interesting, except confirming that samples are now in wide circulation in the industry and mostly seem to be working fine