Yuck.
Did the girls back home like this?
Apparently they did, if I remember right Life showed a picture of the girl back home all happy to receive it and with a glowing smile as she opened the box. First person on the block to have one and all that I suppose.
There was a problem with trophy skulls showing up in dumpsters in later years when families would find them and not know what to do with them.
Japanese gold teeth/fillings were also sought after. Hence the pliers. The GI rumor (maybe it was true) was that Japanese soldiers would Put their money into having gold teeth as a status symbol or some such. Thus those with a tough stomach would have their pliers and check. Must have been at least some truth to it since some people did have whole bags full of teeth. It was also common to cut Japanese fingers off the hands of the dead to get rings. (Particularly on both Guadalcanal for Army units and during the brutal fighting to recapture the Phillipines...)
Military Illustrated - out of the UK - did a great article some time back, it was called "Hard Men of Ancient Rome". In the UK a Hard Man the same as a tough guy/bad ***. It mentioned a third century chronicle of a Syrian soldier (in the Roman legions) who darted forwards, slit an enemies throat and drank his blood. It apparently was good for morale since it got everyone cheering. The same article mentioned other Centurions who kept skulls, ears, human pelts, etc.
My wife chimes in her that her own grandfather, who served in Europe, used to harbor a hatred for Germans and talked about taking their ears. So much so that when she was very young, she thought that the Army must have paid people a bonus for ears... I think it was the CIA's Nung mercenaries during Vietnam who actually were paid a bonus for bringing in ears.
In the American Civil War, particularly in Missouri, guys wearing both blue and gray would also ride around with scalps proudly displayed on their saddles.
It's an old story - taking trophies and desecrating the enemy dead. It happens for various reasons - to spread fear into the enemy, to harden troops, and individually because some people are just what the Brits would call "Hard Men" and want to display their work. (The guy with the necklace of human ears, well you know he can handle himself when it comes to killing... Might be a good guy to have around, at least during the war...)
The most atrocities against the dead, and trophy taking, take place against hated foes, particularly those of a different race or religion. Not as many guys took German scalps/ears because Germans looked like them and there was not as much conditioned hatred. The Japanese were looked on at the time as subhuman and it was felt to be a victory over them to claim their skulls, desecrate the dead etc. At least in certain quarters. Sometimes it also simple gallows human - as famously shown in the scenes in Full Metal Jacket where the Marines pose Vietnamese dead with cigarettes etc and get their picture taken with them. (Stories of dead VC's skulls boiled, bleached and with Christmas lights - the old big bulb style - through the eye socket being kept by some Special Forces soldiers in Vietnam also turn up in memoirs.)
The Army Sgt who was convicted recently? He was the veteran in the platoon, the experienced old hand, and apparently the other soldiers looked up to him/feared him parly because of his human ear collection. Shrug.