I have two questions on the file of USPC Current as follows:
1. I check the file and see that one patent ID could have three different main classes and five different subclass id. Does this mean that one patent can concurrently belong to many different main classes?
2. I match the USPC Current file with the patent file, using the keyword of patent id. However, I find many patent ids in the patent file can not be found in the USPC Current file. I wonder how I can find all the USPC classification for the patents?
Thank you very much for your help!