Hi all

I picked this up this morning in a charity shop - so unusual, I just couldn't leave it there ;-)
It's a good size, 16" x 11" and about 3" deep. No makers marks at all.
Appears to be clear glass below, with the creamy/brown patterned glass above.
I've never seen anything like this before... it's almost organic, reminiscent of leather grain. In bright sunlight, there seem to be microscopic particles in it, reflecting rainbow colours, which I hope are visible in the last photo.
There are lots of little bubbles in it, and in a ring around the middle of the top, the brown bits are in tiny circles, almost like drops of oil on water.
So... any thoughts please?
Steve.