I do know that they were use more than 70 years ago in Taiwan. It was for crushing gold ore but it wasn't used by hand instead the people would sit on long wooden benches and roll them with their feet. The old timer(miner)that owns these said that the women usually worked these things. I did find one pic on the internet shows these being used, probably during the Japanese war during the time when Japan controlled Taiwan. This is the only pic that I can find. View attachment 1243704
Miners stealing gold strange tricks, the most common mode or plug entrainment. According to the old miners said they are using mochi crude gold paper roll into strips and then inserted into the . But one can not plug too much, lest because the of a foreign body, like walking outside the eight will be presented, and it would be caught out. Some miners will dissolve gold dust and mercury or tin together, directly swallowed belly after out, eat fiber rich leek noodles, or eat some of the vegetables dipped in kerosene, you can pull out the gold. As a result, before the sun sets in gold mining companies, gross pit, we fight over, because, from the inside picked up numerous cases of gold. Some miners are the stolen gold, shipped out from other small pit, hidden in secret places. At work, and from the original tunnel out of the pit to accept checks. To the middle of the night, the miners and then slipped inside the dark tunnel to steal gold. Former miners living in poverty, tattered clothes, even wearing sandals start work. But smart miners use mend clothes, the gold hidden in the patch clothes; there are people within the gold into straw sandals, smuggling gold out.
However, aspects of the mine inspection is very strict in the tunnel after the miners work day, the entire people have become dark, pit mouth will set up a pool, we all naked freshen; this time, also check the miners have selfless the best time for possession of gold. Was caught stealing gold miners, was inevitably beat him, even to the police station to be locked up.
Curious that the grinding pans aren't worn smooth like you would expect if minerals were being milled. I guess they could be old and rusted? I'm not sure how effective these would be. The picture doesn't show any mineral milling but I suppose if you set up enough of these you would eventually get some gold.
I google translated the page where you got the picture and it doesn't say anything about milling gold. It does talk about the miners smuggling gold and being um ...inspected.
It would be interesting to know more. This is new to me, perhaps your friend has more information?
Heavy Pans