Most all of the yellow cases cracked with in one to three years. I believe it was due to pour process control on the part of the injection molder who produced the yellow cases. The process they used allowed internal stress to build that did not match with the shrink rate resulting in a crack. The cases cracked just sitting there.
Some people took the top side off and left them separated and in some cases, not all, that kept the case from cracking. Normally it is the top half which cracks but I have seen both halves crack.
There have been a total of 225 Las Vegas yellow caps, 100 Plaza and 125 O’Sheas. I say Las Vegas because the yellow caps were originally designed for use on something at Atlantic City. The yellow caps for the Plaza and O’Sheas were left overs from that project.
Bottom line if you can find one with the yellow case cracked or not just feel lucky that the yellow case is still there. Last but not least, now that you bought it up an un-cracked case should bring a real premium. However, I would not pay a premium because I have been told that some people have figured out ways to color/dye a clear case yellow. Maybe someone will post how that worked out.
Happy Hunting