It might not be legit, but I think you are being too harsh. The second and higher floors of that building have D units. It is not uncommon for floors in buildings like that to be carbon copies. The D unit might just be commercial space and listed separately or not at all. The owner could have removed it from the listing because it was commercial, or maybe the owner of this thing also owns the building. Making a phone is not a poor man's passion project. Secondly, without knowing how they intend to implement this you can't really draw many conclusions. Startup companies don't need huge offices to start with and the manufacturing is almost always in Asia.
From what I've seen in the records for the company, the D is not for the letter after 'C', but for "Derecha" (right). But anyway, this is a big Opus Dei family with bank businesses that registers their "phone business" in a cheap apartment of a simple neighborhood. Nothing against the neighborhood, I live near, but I think they're not coming as sincere to me.
Well, now I've checked a bit around the family and some of them are related to the Rodrigo Rato bank fraud in Bankia. And I think none of them have had anything to do with hardware ever. Wouldn't touch this product with a ten foot pole.
