[Hidden Hippo]

It does appear to be according to the manual. I'll have a look at finding an even more comprehensive set of keys, but looking at the screw itself it could be a torx screw (although none of the normal ones fit), although that isn't too likely since its not normal practice for them.

As for it being changed, I don't think it could have been. I was with it from the time it was removed from the box until I took it out of the shop and the screw was not changed whilst I was there.