alr

I have recently acquired this bicycle for my husband (serial number is K644553). We were cleaning it up today and trying to mount a different saddle to the seat post. I then noticed that not only was the saddle not mounting well to this particular seat post, but it looked too small for the frame as well. I looked up on Sheldon's database and he said that the 82 needs a 26.6 and an 83 need a 26.8. The one we have is a 26.4. My Nishiki Olympic 12 mixte has a 26.4 seat post in it which seems correct, but Sheldon's site says it needs a 26.6 also. So, are all my seat posts the wrong size here?