Around 1950, Breitling was a sponsor and official timer for the major bicycle races, like the Giro d'Italia, Tour de France, etc. There are chronographs with the race names on the dial.

I think yours is authentic and in not so bad original shape. If I were you, I would service the movement and replace the crystal and wear it to honor your grandfather. It looks like it started out gold plated, but you image makes it look very presentable.

Since I suspect there are sellers faking these recently (I am a cynical bastard), I'm testing an hypothesis that there were only a limited number of models and years for watches marked with bicycle races. Does yours have "1190" on the back with a serial near to 7500000?

Caseback script on the first one is incorrect , surely.

Thanks everyone for the info, very informative. I sent the watch to our watchmaker to get restored and make sure everything is working correctly. Once I get it back I'll post the numbers on it and pictures. It's amazing cause the watch actually still works after all this time, the only thing that was not working is the second hand, and sub dials

my watchmaker gave the casing back to me so i can gold plate it, and the numbers on the back are pretty much just as you guys said......... 1190 784495 Breitling in script

cant wait to see how this puppy turns out when its all finished

Interesting that it appears to have the same 'Breitling' script on the back as the Italian piece I posted above. This one is an original grandfather watch. Maybe we need to reevaluate whether this is correct or not.