I found the source of my earlier explanation on springer.com...
Abstract
The British officials who coined the phrase “Made in Germany” intended it as an insult. In 1887, alarmed at an influx of low-priced German products, the British government required goods imported from Germany to be labeled as such. Back then, Germany was to Britain something like China is to Europe or the United States today. It was an aggressive emerging economy with a large store of cheap labor and ambitions to become an economic superpower. But Britain’s attempt to shield domestic companies from competition backfired. Made in Germany became a synonym for quality.1 The story of how Germany succeeded within a few decades still tells us something about the German mindset and tradition.
https://link.springer.com/chapter/10.1057/9781137340542_1
That is a nice legend but I would need to see some facts that support it. I have shown the 1887 Act does nothing of the sort. Legends and myths are repeated all over the place but that does not make them true. Unless and until I can see some incontrovertible evidence I am going with "myth".
Interestingly, Birmingham in England was, in the early 20th Century, well known for making cheap & nasty costume jewellery.
This, in Oz was often sold by the Coles chainstores, & the term "cheap Coles Brummies" was one I remember hearing from my parents when I was a kid.
Even though the source of these things changed over the years, the appellation "Brummies" lived on, although my generation would probably be the last one to recognise it.
Things were seriously tough in Germany after WW2, & some of the first enterprises that got going were those making ingenious clockwork toys.
Some of these manufacturers, fearing lingering bad feelings, labelled their product
"Made in US", followed by, in much smaller font,
"Zone Germany".
In Oz, we tended to take "Made in England" & "British & best" with a grain of salt, knowing the Brits could turn out crap "with the best of 'em".
In Australia, imported stuff, especially tools were normally marked with their country of origin.
When I went to the UK for a year in the early 1970s, a friend & I bought an old car.
Inevitably, we needed to work on it, & bought some tools.
To my surprise, what looked to be the identical set of tools to those I had in Oz, were marked "Foreign", whereas the Australian bought ones said "Japan".