Don't rely on someone else to check your TWH via serial number if you are at possible risk at having a nasty surprise in cold weather. If you have one of these TWH and are curious, the surefire way is to open up the outside cover of your Water Heater, then remove the black plastic panel that covers the board.
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I've marked the picture above with green circles where there are a couple tabs that need to be lifted to open the cover and expose the board. Once the tabs are lifted (careful not to break the plastic, especially if its cold) the cover should just swing open freely but be slightly attached on a couple of the right side wires. You can open this panel without having to disconnect anything. See below for open panel.
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Once the cover is open, take a look at the board. There are a couple very minor differences in the gen 1 and gen 2 boards, in the top left by the power connection. Take a look at the capacitor and diode placement that I have circled in red below. The top half of the image is Gen 1 and the bottom is Gen 2 with freeze protection. This is how you can know for sure which you have.
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For those looking to change theirs out, it really is extremely simple. In fact, if you did the above to check then you've already done the hardest part. After this you simply unplug the cables connected to the board and then plug them into the new board. It's held to the TWH by 4 screws. The wires all come off with little clips and you don't need to rewire anything, just unplug and plug in the clips. The plugs all only fit into one place and if you're uncertain, take a picture of the plugs before you disconnect anything and then reference it while connecting the new one. Changing this out is literally a 15 minute job if you have any comfort level with this type of stuff, and if you don't it's still doable but probably 30 minutes to account for you taking your time.