Rolltop Hidden chair

Hi. I just got this last week because it was interesting. Never saw one with hidden chair and then I found one other here. Searched all over the web and can't find any others out there. Can anyone tell me about these. I am going to change the fabric on the seat as it is definitely done in 70's camper/trailer fabric. But I don't think it is original. The drawers are all dovetailed and the guides are cut into the sides of the them. It is real marble in center writing area. Only one key lock on center drawer. Nicer in person.