I have several pieces of V.Nason which are that style and colour (got my son to check the colours).
Although I've not seen 1 with the dolphin in that position, normally standing on the tail.
I've just checked a Campenella dolphin I have, its eyes are more a protruding applied circle, where as your's are indented.
which again leans more to Nason.
I'm not 100% but fairly happy its Nason