That's what happened with these index cards created from Baltimore passenger lists (NARA publication M327: Index to Passenger Lists of Vessels Arriving at Baltimore (Federal Passenger Lists), 1820-1897--available digitally at FamilySearch).
I have seen the actual passenger list, so whatever the clerk indicated on the back (note the "over" in the portion of the card for "Accompanied by") is information I already have.
This first card is for the father, George Trautvetter. The reverse side of his card was not filmed. I decided to look at other cards for members of the Trautvetter family to determine if they contained the "over" information.
The same thing was done for the card of his son, Michael. No back filmed and no additional comments on the front of it.
Nor was the back of the card completed for his wife Sophia Elizabeth.
Like the card for George, they all indicate that something was written on the back of the card. There were three others in the family whose cards I've not yet located, but those cards also probably have "over" written on them and the backs of those cards were probably not filmed.
Whenever you have an actual document in your hands, it pays to flip it over and whenever your have the image on your computer screen (or microfilm machine) it pays to see if there is a "next" image of the back.
Sometimes when things are on the back of a card it gets filmed or digitized and sometimes it does not.
In this case, I don't think it is probably worth tracking down the card to see the back. My rationale for this is that the card was created from the passenger list, which I've already seen. Anything on the back of the card is also on the manifest. These cards were finding aids for individuals who needed to document their arrival status--hence the soundex order of the cards and the names of other family members on the cards. These cards and the index were not created for genealogists.
If the cards had been created as the passengers arrived, I would be interested in obtaining the backs of them as they could have something not on the manifest. But that's not the case.
