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April 1941. "Sign outside of church in the Black Belt, Chicago." View full size. 35mm nitrate negative by Edwin Rosskam, Farm Security Administration.
This would mean "Are you in the possession of the Holy Spirit." A fairly common expression.
I think it's short for 'Subject', i.e., the topic of this Sunday's sermon.
I assume they meant to write "Procession" but I'm a bit stumped about "Sub." That can be short for "Substitute" or "Submarine," and it makes no sense in either context.
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