A.H. Fox Gun Co. apparently decided to drop the B-/BE-Grade in late 1919. There are two retail price lists, one dated November 30th, 1919, that includes the B-/BE-Grades and one dated December 1st, 1919, with a large price increase and no B-/BE-Grade but includes the FE-Grade double and the M-Grade SBT.
1919 Retail Price Lists.jpg
I have found both of these price lists in the 32 page "A Fox Gets the Game" pocket catalog which pictures the B-/BE-Grade. The "A Fox Gets the Game" pocket catalog that I have with a 1920 retail price list is 36 pages and doesn't picture the B-/BE-Grade. We do know from the records and observed examples that a few B-/BE-Grades were made well into the 1920s.