Help identifying Chinese mark on pendant

I've had this a while, bought for resale but it didn't get that far and it's mine now It was described as vintage but no other info, just curious about how old it is and what it's made of. Thank you

 

Looks like a Chinese Bi Disc necklace pendant but I wonder if it is some sort of toggle or button? I am having a hard time seeing the hallmark. Could you take a close up?

 

They are good luck symbols on the front 長命貴富 - long life and wealth

 

It is shaped like a cash coin.
The mark on the back looks like one of the silver marks, but it is a bit blurry. It is best to have it tested.

Bi discs have round holes, because they represent heaven. Cash coins represent heaven and earth, heaven is symbolised by the circle, earth by the square in the centre. So earth surrounded by heaven.

 

Thank you for all the replies. I will try and get a clearer photo of the marks on the back, it's too dark and murky here atm