Post office customer desk brass inlay

This is from a customer desk at the 1936 Riverside California post office. This office is amazingly preserved. The maintenance staff has not marred or altered the structure. The spheres are covers for holes that appeared to be well or containers. I wish I knew what the numerous slots or wells are in the brass inlay. They are in all 5 of the customer desk/tables. No one at the post office knew the past use.