cut out the shape to desired size - my one is 10cm but i think 5 is probable about right as mine is a bit big.

Sand the surface of the disk with fine pad or scotch pad and clean with water and dry with cloth.

spray the gold paint. you could also hand paint if you are not set up for or happy using spray 

leave to dry

Cover the disk with watered down acrylic brown paint.

Make sure you get the paint into all the etched details

Carefully remover the paint with the cloth allowing the etched areas to stay painted.

you can do this as many time as you wish to build up an authentic weathered look or just keep it bright gold.