Solar Equipment identifying markings

[eeprom]

Hello,
I have some PV equipment (junction boxes), and on them I have 4 markings:
1 - triangle with lightning bolt == shock hazard
2 - TUV == a EU certification
3 - IP65 == enclosure rating
4 - 2 square boxes, one within the other.

What does the square box thing mean?

thanks
EE

 

[davidbeach]

Double insulated.

 

[eeprom]

Thanks.