These Kialara’s are made of stainless steel instead of aluminum, and are much heavier as a result. They come in two versions, with the differentiating factor being the metal composition of the small bitcoin ‘round’ within the coin; .999 Silver or .999 Gold. All Kialara coins are serialized, with the serial number engraved on the coin, visible through the hologram. The year is displayed in the same way. An interesting fact about Kialara coins is that in 2015, one of them was gifted to Sir Richard Branson by Matthew Roszak, who is a producer of The Rise and Rise of Bitcoin documentary.