The sat-dealers don't know what is inside the LNBs. That's a pity.
Take a 12V battery, connect it to a unknown LNB and place a scanner near searching 25 & 27MHz .
If it is a PLL LNB you will find the 25 or 27MHz signal. If there is no signal its an DRO LNB.
I have checked many LNBs that way in our local stores "OBI, Globus Baumarkt/Euronics/Expert..." without any problems by the staff
73s DB8TF