I've just bought a Mamiya-Sekor E 50mm f/1.7, which is in tip-top condition, except that the lubricant seems to have gone hard. The focus ring is extremely stiff. I want to clean out the old gunk and replace it with new lubricant but I don't know how to take this lens apart safely, and so far I haven't found much online.

Has anyone else had experience with this lens?

Thanks,
Jonathan