Certainly looks like an adze, although the few I have owned, had a curved back.
When you used these to "dress " timber, you were left with small characteristic marks - you could always see they were adze cut.
I think Dannyr might be right - this could be for fine final dressing.
A beautiful tool that needs a razor sharp edge !
When I was first introduced to using an adze ( rebuilding wooden bridges in Western New South Wales ( Australia ) , I had to put both feet inside a small metal drum - less painful than cutting tendons ! The timber used for bridge building here are harder than almost anything seen in UK
That's a nice piece of gear - the handle needs to be the right shape.
By the way, it takes a few years to learn the craft of using an adze to it's full potential - so I am sure it will give you challenges and rewards