I have four of these and they weigh 34.5 grams each. They are around 0.130 thick instead of .120 like the silver rounds. Really strange weight no matter what they are made of. And the edges are reeded but I can't tell from the Chipguide pics if that the ones they show are also reeded. Based on the added thickness and weight I think these have to be .999 silver also (I made a mistake measuring them before). Are you sure yours only weigh 31.1 grams?