I try to identify technology fields of patents in developing countries. Overall, I was able to do it, except for IPC G02G. It was said that "IPC code unknown for G02G". Does this mean that G02G is a typo?
Subclass G02G never existed in the IPC. Class G02 contains three subclasses, i.e. G02B, G02C and G02F.
An “inventory of IPC ever used symbols” till version IPC-2018 (valid and deleted symbols) is available from the Download and IT Support Area of the WIPO IPC website.