The Compur shutter was the original choice for the Hasselblad lenses (the C series, both the T* and the earlier non-T*).
When it ceased production, they switched to the Prontor shutter, and made other changes in the mechanical design that resulted in the CF product line. Most of the CF lenses are optically identical to their C T* predecessors.
The /M versions of the SWC and the 500 have user-changeable focusing screens.
In the earlier non-/M cameras the screens had to be changed by a technician with suitable instruments to set its position.