He looks like a campbells, and from what I've seen of that kind of dwarf, they always appear to look a bit chubby and well rounded. Of course it appears your hamster has his cheeks full of something since they look a bit puffed out.. which I think is making him appear chubbier then normal.
I'm sure he is a fine healthy weight so long as he gets enough exercise on his wheel. Syrian hamsters can range in size and weight, and I'm sure this can happen with some of the dwarf species as well.
If you can find a scale and weigh him I would do that. An accurate reading would probably allow some of the experienced hamster owners here on HC to tell you if hes in good shape or not.