From the outside
Typically a rev F board Color Computer 1 (or TDP-100 or white "64k Color Computer") will have the Color Computer logo centered above the keyboard, but this may not be sufficient to fully identify this system from other CoCo 1 systems.
From the inside
It will be necessary to open your CoCo 1 (or TDP-100 or white "64k Color Computer") to examine its mainboard. There will not be a board revision marking (on other CoCo 1s this is often near the cartridge port) and the most important identifying characteristic is the placement of the 6847 chip almost perfectly centered next to the center plastic post of the case, circled in red in the photo below.