Long story short: Proteus never actually manufactured goods so much as it much more acted like a parasite before 2063. Until then Proteus had a large network of agents, holdings etc. in place that enabled it to funnel funds from various corporations into its own accounts. Proteus was largely owned by Euro-corporations and doing basic research with mostly trans-human goals (making humans capable of sustained live in deep-sea or space environments etc.).
It all came down, when Proteus tried to screw Ares with the same spiel. Ares lost a couple of high-value assets and Thor-hammered an arcology of Proteus in 2063, then demanding a corporate court Omega-order against Proeus. That didn't happen, as SK stepped in and told everybody that Proteus was going to be restructured. The process started and then the Crash 2.0 happened, in which Proteus emerged stronger than ever. In 2070 they're pracically a normal AA-corporation, but with huge marine and aerospace assets, as well as magical and biotech research. They could be a AAA, I guess, if it weren't for their past and their lack in matrix services.
