Thaler

I apologise in advance for my ignorance about coins. I am accidentally interested in coins, and not really very knowledgeable. I was given a collections of coins by an uncle who spent some years in the Merchant Navy sailing between the UK and as far as Australia, before he returned to work in Salford Docks (closed in 1982). So it is mostly a mixture of early to mid 20th century low denomination coins, with nothing really unusual or of great value and almost all of which are easy to identify using the internet. However, one item which has me beaten is the attached. It is a round brassy type piece around 27mm in diameter, with a squarish hole. It is similar in style to some of the Chinese coins, but the patterns are not Chinese characters. Is it a coin, a token or something else entirely? There is a small hole punched in it (at the top of the pictures), so it may have been adapted for use as a pendant. Any help or pointers would be great as I have been unable to find anything quite like it.