I am sure this will not be the first response to your query, but . . . The 'DO' means ditto. I have also seen it in small letters and in cursive. Can go on for pages and pages. Some enumerators used our more familiar " to indicate ditto, as we do now. (An advantage of using microfilm where you are forced to go page by page instead of going directly to the page needed is that you notice things like this.) Good luck with your research! Leslie in LA