Clear finish on walnut desk

I recently purchased a large walnut desk with a center drawer and four drawers on either side resting on claw feet. I believe it is walnut and the colour is a light french walnut (about the colour of jack daniels whiskey). The top surface has a clear finish but there are small cracks throughout the surface about one to two inches long underneath the top coat and above the wood surface. The clear finish seems to be built up in layers. Is this characteristic typical of lacquer? What causes these cracks to occur? The desk was made in 1951.

I was also wondering if I were to refinish this desk if I could sand the surface down eliminating the cracks without touching the wood to apply new clear finish? Will lacquer (if this is the clear finish) adhere to old lacquer?

Your thoughts are most appreciated