4V Train Whistle electronics

[Rene Rechthaler]

Hello, I need help numbering (and composing) a part...
I dont have the physical part but got good pics from Ddriver, so the part itself is nearly done.
   
Part(s) in question: x871a/b
http://www.peeron.com/inv/parts/x871a
http://www.peeron.com/inv/parts/x871b
https://www.bricklink.com/v2/catalog/cat...a#T=C&C=12
https://www.bricklink.com/v2/catalog/cat...b#T=C&C=12
https://rebrickable.com/parts/upn0313a/c...functions/
https://rebrickable.com/parts/upn0313b/c...functions/
from the outside, its the same brick, but the B version has some electronics inside to reverse it.

Now the big question: how should that get split (and numbered)?

Its consists of base (black) electronics (dark tan) and cover (clear)
BL and Peeron have the main (paintable) color clear and the base is hardcoded black.
I would use u9618-20, each in a and b like the microphones u9616.
a is the older Forward/Stop and b the newer Forward/Stop/Backwards
Should i use u9617 for a split microphone bottom?

René

[Rene Rechthaler]

I am nearly finished now...
   
left the older a and right the newer b
size and connections are the same, but i got better pictures of the b, so the electronics are modeled there.
for display purposes, the tops have been painted clear, but would be color 16. (why does LDPE doesnt like clear things in bfc mode?)
name: u9618a/bc01 Electric Train 4.5V Whistle Control Block 4 x 8 x 2 Forward/Stop(/Reverse)
consisting of u9618a/b (Top), u9618a/b (Base, black), u9620a/b (Circuit plate, dark tan)

Any more things to be considered?