It is quite interesting, do you have photo taking by this lens?An incomplete and purchased for parts, german[not singaporean] rollei a110 provided the lens for this"body cap" adapted optic. to achieve perfect infinity focus some shaving of the body cap surface was necessary prior to screwing the nicely made brass housing down .
it has a nice toothed edge and enuf "travel" to be turned from infinity to about 4 inches . its pretty good at normal distances but with extreme shallow focus it gets glowy and less contrasty .
i suspect this is because of the exposed brass of the inside threads reflecting light around inside the lens ,[and also design?] too small to baffle and the problem does not happen when the lens is 15 inches or more from the subject
the lens itself is a 23mm f2.8 design with "made by rollei" and 3043183 engraved on the lens surround.
its fun to play with and its not bad either.