I looked up "lathe chuck key" to see what you were talking about. After about 20 images of people getting gored by lathes, I have come to the conclusion that it's probably the short and wide T-shaped thing on the side of the big metal cylinder.
looking at some other photos, he is clearly loaded and his initials are "HK". It's definitely Hideki Kamiya who created the comic. http://photozou.jp/photo/slide/3126116/240222215?w=360&h=560
It is a mystery. The uploaders profile name is Hydeqi, he has a bunch of pictures of arcade machines, wouldn't be surprised if it was Hideki Kamiya himself.
photozou.jp/photo/show/3126116/219401531 It's stickied on his profile. I got an issue with your site where the send button is hidden on mobile portrait mode if you type something in the chat box. My phone is Samsung galaxy s7.
The source version of Half-Life is considered "notoriously buggy" by a lot of people. The original version also has lots of mods and an active community, so I wouldn't consider the game "irrelevant".