When you say "Type II" or "1864", I'm assuming the musket has band springs? The tulip-head rod is earlier, but mixups like that do occur, and are accepted by all but the most fussy collectors.

Anyhow, slide the bands forward and look at the rear of the spring mortise(s). SA arms will be cut sharp and square, while modern (power router cut) preps will be rounded.

Your "tip for the day". Sounds like a nice piece and quite a bargain if real.