I’m not very familiar with Simplex’s bells, but I know for sure that Wheelock made/makes some of Simplex’s motor bells, and I’m willing to bet that they make some of the other ones that Simplex sells too.
That may be likely. I remember some 6-inch Canadian Simplex bells apparently being rebranded Wheelock bells. They sounded exactly identical!
Of course here in the states, Simplex would probably use Potter and Wheelock bells branded as they are, since Faraday does not make fire alarm bells anymore. (I think they still make bells for generai/industrial-signaling, but that’s a different story), and Simplex stopped rebranding Faraday’s stuff around the mid-2000s (I actually recall seeing a U-MMT horn-only unit on a modern 4903 strobe plate!)
I’m even reminded Dan M. showing at UAlbany, a renovated sub shop in the campus center extension replaced its 10-inch Simplex bell and 4903-9105 strobe plate with the Faraday-branded equivalent bell and a newer Simplex strobe plate. Then a while back, another Simplex bell/strobe broke down and was replaced with a 10-inch Wheelock bell on an RSS strobe plate (it does make sense, as the campus mainly uses Simplex systems with Wheelock signals.)