So I now have my first experience with Waterlox finish, and am reasonably happy with the results. I brushed it on, but eventually gave up and shifted to a rag. It is a bit unforgiving with drips and streaks, but I think I fixed a few bad layers with some sandpaper. Only time will tell if it will be durable enough to protect from scratches.
One question remains – what type of wood comprises this desk? This desk was once in the Swedish embassy (40-50 years ago), and had since been painted white. Based on some unpainted areas underneath the tabletop, I have surmised that I probably have mahogany here. That being said, I am up for ideas. The wood is relatively soft, and the pre-sanded version had a much deeper color to it, indicating that this will likely darken with time.