In a far less common usage, “Rex R” appears in documentation for certain late-1970s and early-1980s microcomputers (e.g., SWTPC, some S-100 bus systems) as an abbreviation for or a specific model of a Rex expansion card . These were rare, third-party add-ons that extended register capacity or provided additional I/O ports.
I'm assuming you're referring to the REX R, a high-performance sports car. Here are some useful features that might be available on the REX R: In a far less common usage, “Rex R”