determining subs

hi, i am wondering hot can you tell the difference between a sq sub and a spl sub ( techincal speaking) like i want to be able to look at the techicanal stuff for the sub and say hey it is a spl sub or hey it's a sq sub and not have to read through reviews to see if it is a sq sub or not.

higher efficency maybe?
or lower fs?

I would guess most SQ subs are designed for sealed enclosures and most SPL subs are designed for ported.