For the bicep, the source is:
NWN Main Data \ data\textures_02.bif \ Textures, PLT \ pmho_bicepr004
According to GIMP, both the source and the copy are 1.0kB 16x32 Grayscale-alpha, 10 layers
(I've got 1,275 haks in my hak folder, so I can't view haks directly in nwexplorer)