For me this skull is orginal.
Only one thing looks little strange -right pin is connected in strange place but maybe Im wrong and this is correct.
Real deal... Prongs fall off and get soldered back on all the time:-) SA pre-1936,no markings on the back is correct for period.
I was wondering about that myself, Peter. As Bobby said, prongs did, indeed, break their mountings and get resoldered all the time, but this particular one shows no sign of ever being mounted in the proper place to Begin with. It was either originally attached in a sloppy manner(which, afterall, would really make little to no difference anyway) or else it isn't original-but I, too, am inclined to think that it is.
"Much that once was, is lost. For none now live who remember it."