The original Gemini XII Exit hatch from inside along with the “electronic telescope” which is the “L” shaped hardware on the wall to its left. It was replaced later with the Jupiter 2's signature porthole.

Early days

The space ostrich were only in the pilot "No Place to Hide". The lack of chairs below the computers at the viewport is a dead giveaway that it's the Gemini XII from the series' pilot.

Behind the scenes with June

The ship looks smaller than usual here and the walls of the airlock are cut away in a curve. I am assuming this is from the pilot episode and thus it is The Gemini 12 rather than the Jupiter 2

Which works for you?

From the Lost in space pilot: The Gemini XII - later to be redesigned and renamed the Jupiter II.

Put a modular sofa in the curve of the window, add a bar cart and I'm home

The later more built up Jupiter 2 (with the lighting rig visible up top)