The Bohin was made in France and patented in 1937. Its adjustability comes from (a) its reversible head and (b) the shape of the posts which allow you to move the blade from side to side, exposing more or less.

The base plate has it has "De près côté lame" (close shave on the blade side) on one side and "De très près côté lame" (Super close shave on the blade side) on the other.
The posts also have an indicator on the top of them - The De près side is smooth and the De très près side has a "v" in the top of them.
I've found that the only way to get repeatability is pick the side and move the blade across as far as it can go on the posts. Its pretty primitive but does work.

The patent was granted to B.Bohin Fils on 19 October 1936 (published on 12 January 1937) under patent number: FR807430

Bohin Rasoir Bohin Rasoir Bohin Rasoir
Bohin Rasoir Bohin Rasoir

How does it shave?
On the "Super close shave" side its somewhere between mild and low aggressive. There is very little blade feel but surprisingly effecient.
On the "close shave" side its a mild shaver and great for that weekend shave when you are not loking for a BBS.

Bohin SOTD Bohin SOTD