Nazca, the company who created the first Metal Slug, didn't have an official logo, and since they were bought by SNK after the first game, they remained as this. However, the tiles of the first game contain two logos for the company, one static and one spinning. None of them were used in the actual game.

Both of these logos actually show up in the only other Nazca game, Neo Turf Masters.

Stacticnazcalogo Spinningnazcalogo