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The 11A is just the basic "Standard" grade. The Model 11 was made in 11A - "Standard" Grade, 11B - "Special" Grade, 11C - "Trap" Grade, 11D - "Tournament" Grade, 11E - "Expert" Grade, 11F - "Premier" Grade, and 11R - "Riot" Grade. Actually R is the same as the A except it had a 20-inch cylinder bore barrel.
I doubt parts are interchangable between Remington Model 11s and Browning A5s. Maybe during those periods when Remington built the A5s for Browning when Belgium was involved in some of Europe's 20th Century unpleasantness.