[Leica] Universal focusing screen

["Anderson, Ferrel E" <AndersonF@ria.army.mil>]

Before the R8, Leica issued two series of focusing screens for the R series
cameras.  One series was for the R4, and these are not as bright as the
later series of screens.   I don't know when the later series of screens was
introduced, but the older R4 screens are marked on the attachment tab with
R4 followed by the screen number.  The later series does not include R4.

I have the later series universal, ground glass, and ground glass with grid
.  My  impression is that the ground glass on all screens is the same.  

The screen I am interested in is the microprism screen, since I expect that
it should be similar to the SL screen, which I like.  Is the area outside of
the microprism spot ground glass or fine microprisms like on the SL screen?