The oval drop to the lock bolt washer has a southern ring to it. Look in the archives for a smooth bored, full stocked, southern rifle, (with long half round barrel), and it has the same 'sideplate.' I understand that the southern makers favored this type of a washer for the bolt.
This is a nice gun with straight rifling you say-now, that is odd. It looks to be in fine condition and with the amendments specified above, it will be even better. Thanks for showing it to us and for the good photos.
Dick