I thought that your question on the DCC forum was clearly answered. There is no way to visually confuse straight DC light board with a DCC decoder board. No need to look for part numbers.
Straight DC light board has very few components on it. But a DCC decoder board is chock full of electronic components (probably around couple of dozen).
I don't have any photos handy, but even to a most untrained eye, the difference should be glaringly clear. If you could post a photo of both types of boards you have, we'll gladly identify them for you.
