I've just been told about a new golden colour alloy used for this Czech circulating type. The coin still has a magnetic core, but the cover alloy is different now, so that it's conservation will be better over the years.
Further details and exact composition data are still awaited.
(information and image by Petr Barta and Gijs Vlothuizen)
LINK: Czech Mint
Quote from Czech Republic Central Bank website:
ReplyDelete"Technical parameters –
material: steel clad with an alloy of 75% copper and 25% zinc and electroplated with an alloy of 72% copper and 28% zinc; magnetic; 13-sided; weight 8.43 g, diameter 26 mm, thickness 2.55 mm; edge rounded and plain, tolerances: alloy content ±1 %, weight ±0.25 g, diameter ±0.1 mm, thickness ±0.05 mm.
The coin minted since 2012: material: steel clad with an alloy of 75% copper and 25% zinc and electroplated with an alloy of 70% copper and 30% zinc; magnetic; 13-sided; weight 8.43 g, diameter 26 mm, thickness 2.55 mm; edge rounded and plain, tolerances: alloy content ±1%, weight ±0.25 g, diameter ±0.1 mm, thickness ±0.05 mm."
The only difference is:
72% copper and 28% zinc
70% copper and 30% zinc