1916 Bavaria Mi: D28 W, X Or Y?

I would need help to correctly identify this Bavaria 1916 stamp, I have seen that there are 4 different variants depending on the type of paper:
-Mi: D20v color paper
-Mi: D28w, satin yellow
-My: D28x parchment paper
-Mi: D28y plain white paper
But I can't identify it, I discard the colored paper and I would almost also say the white one...
The stamp is actually a mess on the back, someone placed a bunch of pieces of other stamps as a hinge... This brings me to another question, can the stamp be washed and restored by removing the hinges and cleaning stains?

Your stamp is in such poor condition determining paper type is likely not possible. Try soaking it, can't hurt. But here is an image of the 3 paper types, w, x and y from left to right. (Not the same denomination stamp).

I have carried out a cleaning treatment also removing the hinge, this is the result, I think that now I can distinguish thanks to the examples that you show me that it is made of white paper type Y, I think...