GAF
The numbers are still visible in outline.
Long-standing maritime/naval practice to use weld beads to define things like hull numbers and the like.
That way the hull could be quickly painted after stripping/scaling & re-priming. Then, details can be filled in afterwards.
Wartime hull numbers were to be 24" tall, maximum, in white or the palest gray in stock--unless directed otherwise by local Command authority. Subs were often fully "blacked out." As were patrol craft and the like.