if that's actually a bikecycle pannier, i'd suggest it were a front pannier with mesh/breathable sides to carry wet stuff, like clothing or tents.
the original webdomain is for sale
http://overlandequipment.com/
but there is a new website
https://www.overland.com/product/backpacks
same company under a new label?
they're registered at the same address...2145 Park Ave #4,
Chico,
CA