I must confess I'm a bit envious now... If that is real sheepskin. I would probably live in that jacket. Maybe even change my adress to it
Is there a split in the behind bottom of the jacket?
The button concept could be for riding, as already suggested, but it is not a good idea to lift the jacket off the saddle like this in bad weather. You will most likely make an opening in front for rain or snow to gather in your croch, giving blue balls another meaning. For a riding coat to be effective, it needs to cover your pelvis and the saddle, directing water down and away from your seat. Trust me...few things are worse than hours in a saddle sitting on a wet "sponge" of leather and fabric *deleting memories*
Still, the button concept on this jacket might still be intended for this use, and is probably a nice idea when the weather is good
When the rain starts, release the buttons to cover your front of the saddle (and back) and you'll probably have a very nice ride
These are just my thoughts on the subject though...