early M1905s blades were polished in the white , but the hilts were blued includeing a short distance up the ricasso , in WWI the entire bayonet was blued , untill 1918 both springfeild and rock island started parkerizing ,

i think what you are noticeing is simply the differing techniques between the two arsenals , i no longer have my early SA , but i recall it being blued noticably down the ricasso , my RIA matches your description ,