Thomas,
Thanks very much for the info. The nakago is quite rusty, plus I'm quite inexperienced at reading tangs so that accounts for my misreading of the signature. You infer that the date for this particular Tsuneshige might be uncommon, that is very interesting!
I myself think the date is very neat. I like to think the blade was carried in the Restoration a few years after it was made and carried into WWII as well, but I can only be sure of use in the latter conflict of course.
Might you care to give a guestimate on value once I upload better tang pics? Just to be clear, the sword is missing its tsuba and mekugi, has loose and gnarled hilt wrapping, lacks the sarute, and has quite a few dents and some surface rust on the scabbard. As you can see, the blade has seen better days too.
Thanks to the both of you who've replied so far.
Best,
Gunnar