From the catalog pictures it appears Remington offered a more Model 21 --
14810 03.jpg
or late Ithaca NID style --
461815 07.jpg
beavertail fore-end --
Remington Era Beavertail Fore-End.jpeg
For their Parker Double Trap Gun, it appears Remington slightly relieved the rear corners of the Parker Bros. Trap Model Fore-end.
Remington era Parker Trap Gun.jpeg