My chart of serial numbers also tells me it’s a 1948 TD-20. I can see in the photo that it has the old style brass transom clamp pins as opposed to the flipper style that came out in 1949. I’m not sure, but it looks like there may be a little green paint showing from under the other color. The decals look to be from the later TN model, so I’d guess that someone did a spray over with TN replacement decals.