Here are some pics of Gold Crown 1 Slate. This is real original GC1 slate. I bought the table from the original owner he said the table has been recovered 2 times, and nothing was ever replaced on it, so it is the slate that "normally" came with the Gold Crown 1s. This is not to say there is anything different out there, and not to say that every GC1 was installed with this. This is what I am saying is referred to as Brunstone which is commonly found on GC1s and GC2s.
It is hard to get a picture using this square as a measuring device, but that's what I had handy. It reads a nat's ass over 1 1/32.
This is a picture of the underside of the slate. As you can see it is more brown in color, some may call that rust colored.
Most GC1 and GC2 tables have the sloped pockets. This is a top view of the side pocket.
The backing on the GC1 and GC2 slate is full Inch thick poplar, and is usually stamped with a Union Made stamp.
This is a picture of "normal" slate that is usually seen on the GC3s. Notice the darker gray color.
I use my table and slate as a work bench, so the topside is more warn than normal, so it is hard to get a picture of the texture of the Brunstone. It feels more gritty, more similar to sandstone.
I hope this clears some more of the slate debacle up.