But what happens as soon as the coin is mixed with others?
In bitcoin, there is no absolute mixing, since all the inputs and outputs are always known, there are no balances in the chain, only history.
But for an optimal and complementary scheme of separating the value of bitcoin from the value contributed by specific manufacturers of devices for miners, it is just possible to think about creating side chains of manufacturers. In which there would be just a real separation.
If tags were added to each bitcoin that was mined, then you would eventually result in infinite tags to a child coins after used coins are mixed.
Labelling coin is a bit late at any rate, considering 18/21 M are already mined, and everyone can have a record of the inputs/outputs/chain history.