69 fuel tank drain plug

Hey folks,
Curious to know when the change happened on 69 cougar’s fuel tank concerning the drain plug. My former hardtop had a drain plug but my convertible does not. Was this a plant difference or just whatever came down the line?

I believe the tanks with drain plugs are not original.

That’s odd. I’m pretty sure (99%)that the tank on my hardtop was the original w/the drain plug.

Pretty sure most '69s had the drain plug.

Maybe it’s a '69 vs '70 thing then.