Hi Eduardo: Gibsons suffer from headstock breakage because they get dropped; the wood is really thin at the head/neck joint, made worse by the truss rod hole and wekaend furethr by the lack of a volute. Assuming the headstock face has not been mended, as the picture of it looks good, it looks like this guitar had an really clean break without the head coming off. As noted, this is not a "hairline fracture"; it was likely a clean break but not all the way through. It's also highly likely that as the break was so clean, the gap was simply super-glued and clamped shut. Should be good to go if done well. The pictures show what looks like very high action so if this is the case and set-up requires adjustingh the truss rod, be really careful and slow and watch the headstock crack for any signs of movement.
The picture below shows what I bet happened to your guitar (not mine, just a pic from the Internet):
