When the decals wore off my FF Blue fiberglass tank, there were rather obvious marks where they were. I don't think the colour was 'normally in the gelcoat', as far as I know it just was for the fiberglass tanks. Seemed like there was a rather thick coat of clear on it too, but when I sanded off the black paint I put over my gel coat, nearly all the colour came off, but I could still see where the decals were. The decals were also just stuck on, not covered with anything. It's hard to tell what this ebay item really is, but it sure looks pretty original, it would be nice to see it in person, that would be telling, at least to me.
Dave
69S