I received a huge GB from unicomp for international mail forwarding once. It had many of the colours and several keycap sets.
From what I was able to determine: black keycaps (always blank) are all one-piece. Of the rest, they are usually two-piece save for the spacebar, shift, enter, backspace, capslock, numpad enter, numpad + and possibly \| (not sure about \|)
In short, I echo Snoopy.