That is a custom-design engineered steel / wood staircase. It was part of a remodel project in order open up the floor plan and to add a modern design touch that goes well with the given existing build style of the home.
I do like that industrial style interior design and architecture and as the photographer I could take a indepth look at the whole remodeling project for an older home that now looks like a recently designed modern-style home. So, I can't answer questions about the project, please contact the architects for that matter.
This project was part of my on-location product photography, or call it visually documenting an architectural and interior design project (instead of product :-).