Those with 50 equate to 1933 dated price lists, the large one Catalogue 50-F and the pocket 50-F.S. Those with 51 equate to 1934 dated price lists, the large one Catalogue 51-F and the pocket 51-S.
Catalogue 51-F.jpg
With that insert for the Field Skeet Gun, it was probably actually sent out in 1935. For some reason Ithaca Gun Co. skipped 52 and 53 and the next numbered catalog was Catalogue 54 circa 1935. The large Catalog 55 I have is dated Fall 1936 inside and the pocket 55 - S I have is equates to the Price List dated Jan. 25, 1936.
Numbered Pocket Catalogs.jpg
So, why did Ithaca Gun Co. number their catalogs during that four year period?