Japanese back bevels

Pretty self explanatory.

There are several examples in the wild of back bevel/ruler trick on japanese chisels and planes.

In general I go for an uber flat back, but in these cases that would mean a retarded amount of perfectly usable steel gone to hell for the sake of flatness.

First example is on the sides of this chisel, there seems to be a camber on the back so the sides are more ground than the middle of the chisel (which is flat).

The corners are coarser since the 5000 stone cannot touch them.

Another example, this is a paring chisel:

it has 2 micro bevels on the mirror side, one not so micro in fact, a few mm's.

This is another paring chisel from the same lot, this one looks more like a real micro bevel.

They all work. Personally, I like a flat back because I'm more used to the angle at which you need to use the chisel. This is most obvious when you need to pare end grain vertically, say on the sides of a mortise: a flat back let's you keep your chisel 90 degrees to the piece.  

I do need a larger sample size. Perfect excuse to indulge in more senseless consumption.