trunk lid skin - how attached?

Yep factory did it like that, seen many in the last 45 years of being a body man and replacing door skins.
Just a thought before you epoxy prime if your trunk lid is like my 73 Scamp you might want to coat the inside between the 2 skins with something because I know the factory didn't put enough corrosion protection in there. A bore scope will show you all the rust between the panels.
If you tape all the holes up and poor something like POR-15 or what ever you chose to use and coat the inside it will last longer by sealing up the rust.
Just my 2 cents.