I really don't know the answer to this. The Aztar 25 secondaries are a little on the lighter side too. My rack they are all under 10g, averaging probably around 9.5g. maybe it has something to do with that color of green. I know this doesn't answer your question but I was wondering this as well, and more generally the weight difference between all chips in a given set. My uneducated guess would have to be something with the color, or the day they were made somebody dumped a little too much lead in the mix