No, it's not possible to see Buster revision number by software.
I don't believe there was any software version implementation built into the
device.
The one sure way to find out is to look at Buster (U700).
It will have a device number of 390537-xx where xx is the revision number.
If it's an older machine, especially with one of the common revision B
motherboards, it's probably Buster rev 9.
