There were a few versions of the Automats, yours is a K4 also known as the Automat X, the Xenar lens is 1950. The K4A, also known as the Automat MX, has a lever on the front of the lens panel for M or X selection, while your camera's shutter appears to have been modified for M synch and the added studs that Dan mentions above,
I have an Automat K4A, the tell-tale sign that your camera is definitely a K4 is the
Compur-Rapid shutter, those on the K4 only had X sync. The K4A has a Synchro-Compur.
These were the first of the good modern Rolleiflex cameras, mine has a Zeiss-Opton Tessar and is a lovely camera to use, excellent results, your Xenar lens should be equally good.
Ian