It's the Soul of Chogokin GX-48 Big O. I bought it when it was originally released. It's a discontinued model as of now, and for a short period of time there was an exclusive expansion pack for it (included O-Thunder, Hip chains, etc.) ... but it cost as much as the model itself and I didn't buy it in time. That too is discontinued.
Max Factory is releasing 3 Big models this year (and a Figma figure of R.Dorothy). Its Big O model comes with accessories (unlike the SoC model where you had to buy the expansion pack), however Big Duo and Big Fau (!!!!) are just the static models. Not sure if they have joints or can be posed, but it is another chance at Big Duo (only one production run of those existed prior to 2003) and the world's first Big Fau model.
Max Factory is asking $460USD for its Big O, and around $160USD for either Duo or Fau. Big O is coming this summer, Duo and Fau later in the fall/winter.
One other thing... they are 30cm tall. Every other pre-existing Big O model is between 19cm-21cm in height. So the O, Duo, and Fau from Max Factory are not to scale with anything already released from other manufacturers.
Man, I don't have that kind of money to throw around. Half of me wants to just buy the model because it's Big O, but the other half doesn't think it's worth the money. I wish there was a higher demand for them, that way the price would go down a little bit. Alas, Gundam and Code Geass and whatnot have kind of stolen the spotlight.
There is a high demand for them though. The SoC models sold out within 2 months of release from every online retailer. Max Factory is making their release "Japan Only"... meaning they are purposefully driving up prices for the large fan community overseas.