I started out with 3 machine on W7 Home.  I upgraded all of them to W7 Pro through a vendor that not longer exists and was on MS watch list.  I upgraded these through Window Anytime Upgrade.  They all came up as W7 Pro OEM.
 
2 of them are running Windows 10.  I searched online to find out if mt W10 licenses are OEM or retail.
 
So I did this:
 
Click Start then type: CMD
Right click CMD
Click Run as administrator
 
At the command prompt type: slmgr.vbs /dlv
Hit Enter
 
This will indicate the channel, retail or OEM.
 
All licenses show that they are retail,
 
I would be curious of someone is running a W10 OEM and see if the result is the same.
 
 

I'm running the Win10 OEM version and the slmgr.vbs /dlv script reports it as OEM/COA/NONSLP.