The first question is... did you look on the top barrel flat several inches behind the rear sight to see if there is a name or initials, or even partial markings, that could help identify the maker? If anything is there, please post a picture of it.
The old "standby" answer for a gun with a cheekpiece on the left side and the lock also on the left [presuming the gun doesn't have another cheekpiece on the other side of the butt], is that it was probably a cost decision where a left-hand lock was already available, and buying a right-hand lock would increase the cost to a frugal owner... so he opted to go the cheaper route. Of course, no one really knows why we find a "mixed up" rifle once in a while with a cheekpiece and lock on same side... but most shooters want the lock on the opposite side farther away from their face and eyesight.
Shelby Gallien