Strange Census Entries

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The enumerator of this 1920 Campbell Co., TN census obviously had something in mind when he added cryptic notation in the Citizenship column adjacent to apparently selected names.

For example, in that column and in line with some heads of household, he penciled in "M H."  In the case of Oscar Coffee on line 71, he wrote "B. W. F". and on line 73 he wrote "Bd" for John Ledford.  I presume this is to identify him again as a boarder.  Over in the "Mother Tongue" column he chose to enter  "U. S. W." for some of the males.

I've never seen this on any other census.  Perhaps it has something to do with the mining industry?

Please drop me a note if you know what they mean.