As I settle down on the back seat of the bus, I watch as my brother-in-law confidently gets on board and touches his Suica card to the scanner.

Beep beep. It’s rejected — lack of funds.

Not to worry. While he doesn’t speak the local language, this seasoned traveler isn’t fazed. He readies some cash instead. But a minor kerfuffle begins. I head to the front and ask the driver what the issue is. Looking relieved to hear some Japanese, he explains that the shiny new ¥500 coin that my brother-in-law has paid with is simply too new for his bus. It can’t be accepted by the machine.

The issue is small. I offer up a ¥1,000 note, and the matter is settled.

But it got me wondering. When I used to ride the bus as a child around my native Yorkshire, we paid cash. And the cash was handled by the driver, who had a manual change-giving machine and a bag for the overflow.

But assuming that the system in Japan is now set up so a driver never needs to personally handle any cash, it raises the question of why certain items of legal tender can not be used on public transport — or indeed other places.

A quick search online shows that nonacceptance of the new ¥500 coins — the silver and gold colored ones issued since late 2021 — definitely occurs elsewhere. A Kyoto Shimbun article from last year reports the same problem with vending machines and parking meters in the prefecture, for example.

So what’s the problem? Is it the weight? The design? The dimensions?

The Bank of Japan’s website tells us that the new coin weighs 7.1 grams, while the old coin is 7. They are exactly the same diameter, at 26.5 millimeters, and both have ridges on the edge, though these are slightly different on the new coin.

They definitely look different, with the new one appearing rather similar to a British £2 or even bearing a vague resemblance to a €2 coin. But machines surely pay no attention to looks. So it seems to be all about that crucial 0.1 gram difference and those ridges.

In fact, as well as commemorative editions, there are three versions of the ¥500 coin that are legal tender in Japan. The first fell out of favor after it was deemed too easy to counterfeit or imitate, partly due to its similarity to the Korean 500 won coin of the early 1980s.

The other two have partly been the product of efforts to clamp down on counterfeiting, with each having fancier and more impressive security features than the last.

But the number of new ¥500 coins out there in the hands of Joe Public is actually rather low, the Kyoto Shimbun says. As of November 2022, the new coins accounted for only 10% of the total number of ¥500 coins in circulation.

Indeed, when my son asked me to look for one for him when they were first released, it took me a couple of months to find one in my change.

So it begs the question: What’s the use of minting these new coins if they can’t be universally used and you don’t often see them? There are certainly places that won’t take them, and if the government’s aim was to cut down on counterfeiting, their low circulation has surely done little to that end.

But it isn’t just the ¥500 coin that causes issues. Imagine the unfortunate visitor who is handed a stack of ¥2,000 notes by a well-meaning currency exchange abroad (true story; it happened to my parents a couple of times not so long ago).

If you’ve ever seen one of these notes, you’re lucky. If you’ve ever spent one, then give yourself a pat on the back. They were seemingly issued for just a few years and have never been replaced or redesigned.

A Japan Times article from 2004, just four years after the notes were first introduced, described them as seeming “like a novelty to many consumers.” The article, which discusses the “inconvenience” of the bills, suggests that the notes’ high-tech security features had actually worked against them, as many companies had been unable to upgrade their equipment to actually accept the notes due to the high costs involved.

Twenty years on and the ¥2,000 note can almost certainly still be described as a “novelty,” having been left out of the Bank of Japan’s 2024 currency redesign, leaving it looking even more out of place next to other Japanese banknotes.

And with that in mind, perhaps the ¥500 coin is simply history repeating itself. To have a machine accept a coin that is a different weight (albeit just 0.1 g in difference) and with different markings will require either a new machine or a refit — and that costs. Reports suggest a replacement coin selector for a single vending machine would come in at around ¥50,000. The selectors need chips too, so the global chip shortage has done the new ¥500 no favors.

Technological progress is all well and good, but if we’re asking business owners to pay for its rollout, and the public to endure a lukewarm effort to implement it, then it’ll never work — especially as we could quite easily live without either the ¥500 coin or the ¥2,000 note.