Not "rare" and not really slabbed...
A significant element of being slabbed is that there also be a grading applied. These psuedo slabbed chips were presented as examples of what ICG would be doing in the way of offering slabbing services. The plastic holder (hermetically sealed) is what would be used for formal slabbing, but the encased chip bears no grading value and reflects "sample" instead.
These have been discussed in the past (on this BBS) and Slab Free members have determined that these items are not actually slabbed chips. I have two examples of these (AZ Charlies and Tropicana) and I would be interested in trading a Tropicana for one of the other "samples" made up this way.
Jim