The mainboard revision of the SNES can only be definitively identified by disassembling the unit. This is primarily due to consoles being “shell-swapped” during repairs throughout the years. The serial number found on the bottom of the console isn't a reliable way of identifying revisions precisely, but can land pretty closely.

The mainboard revision is silk-screened on the bottom right-hand corner. See below:

“2CHIP” SNES revisions are:

• SHVC-CPU-01 - Serial Numbers UN10-UN18X
• SHVC-SNS-GPM-01(2) - Serial Numbers UN20-UN26X
• SHVC-SNS-RGB-01(2) - Serial Numbers UN27-UN29X
• SHVC-SNS-APU-01(2) - Serial Numbers UN3X

“1CHIP” SNES revisions are:

• SNS-CPU-1CHIP-01 - Most systems have “UN3” serial #.
• SNS-CPU-1CHIP-02 - Most systems have “UN3” serial #.
• SNS-CPU-1CHIP-03 - Most systems have “UN3” serial #.
• SNN-CPU-01 - SNES Jr. (Mini)