Yup, signed Peter Layton piece
Someone must have stuck the knop onto a vase perhaps? otoh, the hole the stem of the knop is stuck into is very small, the width of the knop stem as far as I can see, certainly nothing like the size of the vase opening on the one I just linked to. It's very heavy and has loads of wear on the base but is hollow and you can just with a magnifying glass and held at the right angle against the light, just see the screw end of the knop.
I'm curious about what to do with it. It looks gorgeous with the handle on it- I think I'm going to leave it because the hole opening is nothing like as large as a vase would be or is as above. It's tiny so presumably for a single stem or nothing as would be impossible to clean it. Perhaps the shape is what they call a 'disc' - it looks pretty similar in shape to those pieces, so an early version of? or even what is called here (top left), a 'pebble'
https://www.pinterest.com/pin/521995413033503287/Edited to add:
looking at this listing for a 'shell' piece ,the base colour of the iridescence is the same so presumably the same period i.e.1985
http://www.jvs-en-co.com/a-30357663/english-unica/peter-layton-vase-or-object-shell-reserved/Mine also has a snapped off pontil mark showing and a ground base as does this shell.
I'm leaving the handle. I like it

m