Is this a Korea or Chine Empire coin? [επιλυμένο]

This coin is not mine (yet), a seller is auctioning this one where I often buy my coins as an "unidentified coin".
Usually I can do some easy googling and find the correct identification and then I buy it.
This one I could only get the 四 character, I have no idea what it means, but when I search for it, I get some Korea results.
Any of you experts can tell me the country of origin or aproximade date? I guess with a start I can find the light.

Sorry the picture is from the seller, is probably not in the right rotation though, and I cant get (yet) better pictures.

Any comment will be welcome.





Geison

Korea
訓 - Military Training Command
四 - serial number 4
文 - "mun" (Cash) 1857 ?

Definitely Korea, like @Frenchlover said
Mid 19th century for date, and those photos are in the right rotation.

Closest:
https://en.numista.com/catalogue/pieces47282.html

Thank you a lot again bright minds of Numista!

I didn't have any from Korea, now I have +1 issuer.

Solved!

Anytime!