What shape are the pieces of glass your mate found?
The flat piece in your first pics is the reflector plate from either a Revi C/12A or D (as Andy said) or Revi 3d gunsight. Ahead of this there would have been a similar shaped Tinted glass plate.
The sight in that instrument panel shot is a Revi 16B.
In addition to the Tinted glass and Reflector plates, there would have been 3 circular objective lenses - one with curved top, flat bottom (like projector lens below), one double curved, and 3rd double concurved - aswell as the Sighting image lenses, 2 for Revi C/12D, 1 (I think) in the Revi 16B. These were also shaped like the projector lens below.
The long rod may have been part of the sighting mechanism for the Me 410 (or Ar 240?) as mentioned, or possibly part of a ZFR (Zielfernrohr - telescopic gunsight) -3A or -4A, which were apparently tested on various aircraft.
Pics:
1: Slide projector lens.
2,3: Revi C/12D
4,5: ZFR 3A
6: KG 13B control columns
7: Bauart made KG 13B
(pics 2-7 and source of info: 'German Aircraft Interiors 1935-1945 Vol. 1' by Kenneth A. Merrick)
(clashed with Sander - good stuff mate!)