Im no expert on these but Jon has 5, and they are all quite different in stly and colour, like your 2 fish one he has a large one fish which is made with what looks like 2 pieces of glass pressed together, and a smaller one fish which is almost identical to this one.
I would definitly say both of yours are Murano just different makers/styles
If you type Cenedese there are quite a few on ebay here is quite a nice example http://cgi.ebay.co.uk/Massives-50s-60s-AQUARIUM-GINO-CENEDESE-Murano-/290444094794?cmd=ViewItem&pt=Glas_Kristall&hash=item439fd12d4a
They come in different shapes, colours, styles, sizes, amount of fish and so on, It appears the more fish the better and obviously the bigger the better
But a word of warning there are alot of chinese fish paperweights/blocks and so on but you can tell the difference because of the quality (not so easy from a picture on a computer screen though)