In the Trek universe, the Latinum is a mercury-like liquid that is encased in a gold shell of 4 or 5 standardized sizes. I own 3 of them.
Memory Alpha recognizes 4 sizes: Brick, Bar, Strip, and Slip. There has been numerous discussions as to the value of each in real-world Dollars, but this will always be difficult at the economics of the future are fluid, much like the actual economy in the real world. However, there are numerous, and sometimes inconsistent, examples in DS9 where a character will say X amount of Latinum will buy you Y amount of goods or services.
These are 6 screen used Bricks of Latinum. There were numerous ones made for the Season 6 episode "Who Mourns For Morn?"
This is a 'bar' of Latinum.
This is a 'strip' of Latinum.
There are soooooooo many recastings out there, that it can be difficult to tell the real from the fake ones. For this reason, I have spent perhaps more than I should for screen-used without regret. Even more strange is that the cost of purchasing screen used Latinum has increased by almost double over the past several years to the point where it costs almost as much as real gold!
Perhaps I will just stick with the 9 pieces I already have, thank you very much.
Also, don't worry costume enthusiasts.... I have more Ferengi costumes coming.