7. What is the IP55 protection class made up?

There are various German and international standards for the IP codes.

DIN EN 60529 (VDE 0470-1): 2014-09 Degrees of protection through housing (IP code) (IEC 60529:1989 + A1:1999 + A2:2013); German version EN 60529:1991 + A1:2000 + A2:2013, formerly VDE 0470-1[3]
ISO 20653:2013 Road vehicles - Degrees of protection (IP code) - Protection against foreign objects, water and contact - Electrical equipment describes the current status for road vehicles with extensions to the coding of the protection class compared to previous DIN standards.

All standards are valid, but differ in their revision status and details. When specifying IP codes, it is necessary to specify the reference standard for clear coding.

Since the meanings of the protection types within the respective standards have also changed compared to previous editions, it is also necessary to always indicate the number and publication date of the standard in order to establish a clear reference.