I've owned Seamasters with Alpha hands before. They seem to be an unusual option Omega used in the late 50's to early 60's automatics. Here's a 1960 caliber 591 (the temporary replacement for the 50x series before the 55x/56x took over):
Yours has the same style second hand to so I'm inclined to say all 3 are original to the watch, or at least a correct matching set.
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