OK, just did some "Walk Around" research on the Mirage III. I confirmed a suspicion I had, will now suffer nightmares for weeks and may lose much of my hair... but have valuable info for anyone modelling a Mirage II.
The main and nose gear doors are rigged in a manner virtually identical to the Dassault Falcon 20's I worked on. After shutdown, the doors will remain locked up, unless released from the mechanical locks. Releasing the doors is needed to properly inspect the various components installed in the bay. On the Falcon 20 (CC-117) we would do it a couple of minutes after shutdown once the pressure bled out of the hydraulic systems. I actually found a picture that shows virtually the same switches and door uplock I am familiar with from the Falcon. Might actually be the same part in the case of the switch.
Feel free to build with doors open or closed... both are right. :)
The nightmares and hair loss I will explain if anyone wants to know just how the Falcon (and presumably Mirage) landing gear retraction sequence works. :)