Early French Air Service Clock?

This is a link to a recently completed Ebay auction for an early - WW I? or early 1920s? - clock that has a dial marked with French air service markings. The clock is in very rough condition - kind of a basket case/parts item - but from what I can see of the dial the markings on it appear to be right. Also, the leather case seems to be right for the era as well and appears to be the kind that was used by the men who went up in observation balloons.

My question on this has to do more with the movement and wondering whether it is correct to the dial. I can not read all of the inscription on the movement, but the writing opposite the winding stem reads, "Automobile Regulateur" This makes me wonder. The three possibilities that I can come up with are: 1) the movement is not original to the clock and was replaced at some point in its life, or 2) the movement is original to the clock but this was not used in a balloon but rather in a staff car that was assigned to an air service unit, or 3) the movement is original to the clock and this is the result of wartime or early post-wartime shortages where they used anything that was handy, including a movement made for an autobile clock in a clock that was issued for use in a balloon.

Does anyone know which of these three possibilities is correct, or if there is yet another explanation that is the case here?