It is very hard to date catalogs since most are not dated so I have tracked down the date of the Saturday Evening Post magazine shown in the scan on the far right top. It was created by E.M. Jackson for the 5/14/1927 issue. That coupled with the letter above center helps date these pages to 1928. I'm sure Manning Bowman sold this line for a number of years so many items in this line could have been sold years earlier.