Sony ILCE-7RM3A (Alpha 7R III A) is the “A” version of the Sony A7R III (7RM3), not a different camera generation.
In simple terms, the 7RM3A is a slightly updated version of the A7R III with the same core specs—around 42.4 MP full-frame sensor, strong autofocus, and high-resolution still photography performance—but with a few minor hardware improvements. The main upgrades are a higher-resolution rear LCD screen (about 2.36M dots instead of 1.44M), a revised USB 3.2 port for faster data transfer, and removal of the Sony logo under the screen. The sensor, image quality, and overall performance remain essentially the same as the original 7RM3, making it more of a refresh than a new model.