hello Steven, and thanks for your interesting reply, and I will now have a good idea of what to look out for as a 'third' part to my bowl and plinth. I found this yesterday at my usual winter boot sale, and tend (perhaps wrongly) to believe that these sets should always be in three parts - at least you'd certainly need a dome/frog if you wanted to us it for flowers.
Possibly for reasons of scarcity, I see very little Jobling art glass on my usual travels - and some of the pieces showing in your flickr album are to die for, particularly the opalescent :mrgreen: I have only ever seen one non-black plinth (Bagley in fact - green) - although I have shed loads of the black ones - they seem to jump out at me on Sunday mornings wherever I go - I must have thirty odd - but always pick them up since they might one day be useful.
Hopefully, I will have a copy of the Tyne & Wear CC Museums publication soon, which will help. Thanks again