As a newcomer to coffee enthusiasm, I am still discovering new things every day. For example, I discovered the Phin Vietnamese coffee maker, while searching for information on something completely different. And that got me thinking.
I was actually looking for information on the Durobor monofilter. This is a metal drip filter for a single cup of coffee that was in use in Belgium until the 1980s (Durobor is a Belgian manufacturer which continued to produce glassware until 2019, when it went bankrupt). If you went to a café and you asked for a coffee, you almost always got such a filter. As a child, I never knew anything else. Later, those metal filters were replaced by plastic ones with the ground coffee already in it (vacuum-packed per 10 pieces). As you would expect, the quality is not at all comparable.
A photo of the Durobor monofilter can be found here (this was before I even had cleaned it, so you can see what excellent condition it was still in). I was able to buy this one at the flea market in Brussels for only € 5.00 ($ 5.86 or £ 4.27). I had to walk around for almost two hours before I could find such a pristine specimen. This one is in stainless steel. There are also silver-plated models, though usually in much worse condition.

But now you must admit … this is very similar to the Vietnamese coffee maker in terms of both design and method, isn’t it?

Coffee was introduced to Vietnam by the French in 1857. But after the Vietnam War (1955-1975), coffee production was limited due to governmental restraints which limited private enterprise. It wasn’t until 1987 that privately owned enterprises were permitted again. Nowadays about 97% of Vietnam’s coffee comes from Robusta.
So I think the Vietnamese took the Belgian model of the monofilter and adapted it to become the so-called Phin. But is there any proof of that? Because, of course, it also could have been the other way around. What strikes me in any case is that you find a lot of information about the Phin, but almost nothing about the Durobor monofilter, which has been almost completely forgotten.
EDIT
When I was looking for pictures of the Durobor monofilter, I came across a model that was in use in the 1970s. It was not made of stainless steel, but of aluminium, and the handle of the glass holder was (I think) made of Bakelite (another beautiful Belgian invention).

And now I remember that my paternal grandparents used these cups. I don’t remember the filter itself. They didn’t need it, because they made coffee with a porcelain Melitta with a paper filter in it. And later they used an electric coffee machine. I think my grandfather also took such an aluminium cup to the shipyard where he worked. There, he drank his coffee from a small thermos.
In the picture you can see the aluminium model from the 1970s. I don’t remember ever seeing this model in cafés. It was probably a simpler and cheaper version for home use.