Ca.1945-1952 which measures 3-1/2" x 6-1/4" closed and fully open is 20-3/4" x 12-1/2".One side fully open pictures 12 variations of the Model 12 with descriptions of each.The other side has a Model 12,14" long,across the top with features described.there is also a spec chart and shotshells featured.The code n the back cover is "Form No. 1878". Excellent condition