I noticed that these lenses did not appear here, so I add some pictures.
The lenses are really tiny, much smaller than pen f ones, for instance, and prone to flare (things get better with the telescopic hood at the deeper position).
The 4cm lens has low contrast at f/2, but put a +1 in contrast and it gets better (digital advantages).
The 3.75cm is less than 1cm deep when focused at inf and is beautiful!
Both have a nice vintage character and beautiful color and contrast (especially the 3.75cm, being a Tessar).
Here is the Biotar (1/2):

Tessar (1/2):

You ought to post sample pictures taken with the lens and m4/3, or I will have to move this thread to another board.