Yes.

Zippo lighters do have flat bottoms. Flat engraving refers to the Zippo factory engraving directly on the lighter body. The words are single or double circles. There is no raised engraving method. It is the flat engraving that comes with the mold. This engraving method makes the words flat, without bulges, and consistent with the lighter body. I own a 1964 Zippo lighter with words engraved on the bottom, which is flat.