I started collecting them years ago and took a pause from collecting for a few years due to illness. For me it started as trying to get a coin slabbed by every grading company. It is not that easy. For example I used to have a Franklin set that was slabbed by Hallmark. I cannot even find any coins around now that are still in their Hallmark holders but I know there are plenty out there. Then I discovered sample slabs and started collecting those too but there are some that are so scarce one could never hope to own them regardless of the low prices for them. I still am trying to build that set of slabs from each TPG and am just starting to look again. Cheers!