These Scott 250xx are not the same as you can see by the pictures .
To me there are only three reasons for it...
1 - Every postal office had a cancel type that the post office regulated and ordered as close as regulations would allow.
2 - If one post office precancel machine broke, they would borrow from another post office.
3 - Or as machines broke, the newer machine brought in were as close the the original as the old, but different.
Ignore the rulers I used, they are not in MM, but are used by me to identify differences at the beginning of my investigation.