Andy,
It is not a standard Mercator projection. It looks to me more like a Hobo-Dyer Equal-Area projection.
There are a number of non-standard projections that each claim to provide a more accurate notion of actual land mass and area, but the geo-political implications are vast, and account in part for their minimal popular adoption. Each projection has a strength and weakness.
During the Cold War, a number of alternative projections made the former Soviet Union appear to have a
much greater land mass than shown in traditional Mercator projections, and were squelched in the US during this time for political reasons.
For a fairly comprehensive presentation of alternative map projections, see:
http://en.wikipedia.org/wiki/List_of_map_projectionshttp://en.wikipedia.org/wiki/Category:Cartographic_projectionsI can spend hours looking at these things...and have! My walls display a few of them.
Best,
Dan. (...who has always been a map-gazer)