This is the grey Whooper Swan variant that was in production starting 2004, but the production of which was not continued at Iittala in 2014 when the whole bird production moved from Nuutajärvi to Iittala. 
The production of the white Whooper Swans has continued until these days, so those are far more common than this grey variant is.   
The design of these birds is by famous professor Oiva Toikka. 
This bird is unsigned. 
Normally these swans are signed with a running number followed by the year in which they were made, just like the white ones are.
This individual is very beautiful with a well formed feather pattern and the reason for it not being signed we have not been able to figure out.
These birds are presented in the new book "Toikan Lasilinnut - Toikka's Glass Birds" on page 125.
The last pictures show this bird swimming together with a white Whooper Swan of ours that is for sale elsewhere on this site.
Signature:  UNSIGNED
Condition:  Excellent
Size:           325mm x 195mm