The cut through the middle layer goes from the right end of the white "Greenhill's 1" sticker to the left end of the long red sticker, cutting the middle layer into two triangles. You can't see it because the cut ends at two corners of the middle layer.

It's a modified Square-1.

What amazes me about Mr. Greenhill's work is how smoothly the corners are rounded. Far as I know you can't just walk into a store and buy pre-fab pieces like that. You have to either cast them or hand assemble them in some manner. Either way they look so factory finished. Incredible craftsmanship for custom made pieces.

I was thinking that myself...
Now it all became clear.
Thanks,

Vadim

Anthony never cast the pieces. He uses sheet plastic to make up each piece individually.
Isn't it amazing? I would love to come for his open day in the workshop just to see how he does it... it's just that Anthony never has open days. Shame inn't it?
Vadim