Some of the white(portal) panels have labels consisting of numbers and/or letters. I've only noticed two of these, maybe there are more. One of them has the code 50414E454C205359595354454D on it. This sequence of characters translates in the hex converter as "PANEL SYSTEM". There is also a variant of panels labeled 5748495445. In the same way, the code is translated into the word WHITE, which obviously indicates the type of panel.