Steve,
That is definatly a home made version and extremely well thought out one too. This is the definition of an assassination's or subversive mission (S). It is these types of BoobyTraps that came out during WWII and with the advent of stronger batteries during WWII you could make a very significant good BT.
Are there any leads on it or even with the wiring that may show any kind of rust?
My three thoughts for this type of weapon, is that it was used to either assinate a High ranking officer. Not so likely though?
Secondly, is that the device being as small as it is was given to or left behind in someone's house or businness to kill just one victim. Usually, a book that the recieving person may love or was looking for it for a few years. More likely.
Third, it would have been used to boobytrap a house where the Russians had once occupied and that this one wound be laying on a table at such an angle that it would look like it was going to fall off. Or that except for the book laying on top of it. This because some of us have a fetish or whatever you'd call it for people who hate to see things that are out of order into a way back into order.
With that being said, I believe it was specifacly used to take out one target (Person) only and was used by the Russians or Germans for that purpose. Too small of a trap to be used for anything other than to kill the one that opens it and maybe another person who is too close to the detonation.
There are so many ways to harrass your enemy with an infinite ways to BoobyTrap anything? The only limitation to Boobytraping is the stretch of the human brain.
Also great Trunk Monkey you have there!
JFYI