I believe this may be a prototype. See slightly different wording on OWI No. 51 "If you tell where they're going...".
Small tears, pinhole in center of folds, and pencil marks as noted below.
"W.D., A.G.O. SECURITY POSTER" with quoted "Embarking" inserted in pencil before "SECURITY".
Crossed out in pencil:
"OWI Poster No. 51. Additional copies may be obtained upon request from the Division of Public Inquiriew, Office of War Information, Washington, D.C."
"U.S. GOVERNMENT PRINTING OFFICE : 1943--O-515025"