How can i tell which Amlogic S812 box i have

Hi to all, just coming over from openelec .

Could someone please explain how to tell the difference between an 8S and a 8Splus ?
as im looking to flash two of these boxes i have.
(looking for a Libreelec for these boxes and a working remote

I bought from Amazon UK
here
ACEMAX OpenElec Linux Pure XBMC KODI TV Box 2G RAM 8G: Amazon.co.uk: Electronics

thanks in advance