It's the shiny shine, they like to play, stick it in the safe and leave it there, or better forget you have it in the safe and keep buying more.
I don't care for tarnishing but don't care for the " mirror finish" either. I love the Engelhard 100 oz bar compared to the sunshine 100 oz bar. Silver a little more in its natural color.. I'd love to trade my sunshine 100 for another Engelhard..
My favourite, and I do not know why, maybe because I don't have one is the 1 kg Perth Mint Extruded Bar. kinda has a Matt silver look, flat but with rounded edges, probably a bad analogy but looks Aston Martin ish to me, cheapest Aston on the planet.