I feel like this ought to be a FAQ, but because of the abundance of articles on Grade Point Average coming out of the US, it's extremely difficult to search for. I have a micro switch with rather difficult to read labelling on it, but which clearly shows a current rating of 0.1GPA (and 125 VAC): I'm used to seeing a simple 'A' after current ratings. What does the 'GP' stand for in this instance?
To really know, you'd have to have a few hundred dollars to get access to the CUL 61058-1 document. However, it probably stands for General Purpose Amps GPA. The rating is the same as a regular amp, they probably redefine it to differentiate between DC amps and AC amps or to mean both.
Bottom of page 17 of this Farnell document defines it as “GPA – General Purpose Amps (Inductive Load)”.