Interesting that Researcher's first letter dates to October, 1932.
The 3 1/2" Magnum-Ten Super X shell with 2 oz. of shot appeared in the April 1, 1932 Western Ammunition booklet.
https://www.doublegunshop.com/forums/ubbthreads.php?ubb=showflat&Number=304065

I wonder if Mr. Biggs slipped the new Western load in his Flues 2 7/8" chamber 10g?