Ron,
No.3 blade is clean.. (condition of ji hada is much better than No. 2 Shinto) But the nakago tells the truth. Even though the pictures are grainy, you can see that there is a lot of age in the last 3.5 inches of the nakago in comparison to the top 2 blades (youngest).
Alex,
There were often shinshinto copies of koto works, not as often in shinto times. So no 4. is definitely not shinto.. The bottom blade is obviously kamakura (using sugata, kissaki, and patina on the nakago) and the oldest of the lot with an nice patina on the nakago.
Of course these could all be master forgeries and we could all be way wrong!! But I'm just going to throw the idea on the table that all 4 of these swords are probably somewhat important works and authenticated as un-tampered with (age considered ie. patina etc.).