Bren Sights
The sights on the Bren LMG are offset to the left precisely one inch. As mentioned, this is to allow sighting around the top-mounted magazine.
To avoid any tendency to crossfiring as the range increased, the gun was always zeroed to impact exactly one inch to the right of the sights, meaning that line-of-sight and line-of-bore were PARALLEL at all ranges, instead of converging at any particular distance. Convergance would lead to crossfiring, and inaccuracy at all ranges except the point where lines of bore and sight crossed.
The short-range zeroing target had TWO targets printed on it, one being a normal bold-printed aiming mark and the other being a "shadow" or lightly-printed version of the bold target. The gun was aimed at the bold target, but actually zeroed to bring the impacts to center on the "shadow" target, which was, of course, ONE INCH to the right of the bold bullseye.
The gun was extremely effective, and the offset sights were no great concern at all. I'm a left-hander, and even I had no difficulty putting rounds on target. I just wish I could import the Bren that I still own in Canada, into the USA. I paid $325 for it thirty years ago, and it's worth about $40,000 if it were a transferable gun in the US!.