The item is made of what's termed 'filled resin' or 'cold cast resin'.
It's a resin loaded with fine particles of brass or copper 'dust'. When cured it forms a matrix of metal particles embeded within the resin and can be polished to give an appearance close to metal on casual inspection.
https://hackaday.com/2016/07/14/lear...-cold-casting/
A slightly similar process is used in sintering, although this uses fusing rather than resin to bind the material together.
https://www.powderedmetalparts.com/s...d-metal-parts/