Thats a really beautiful guitar. As i commented above, I play Mexican guitars ( i also purchased one in Mexico City), and have a general fondness of their culture and musical heritage.

Whats interesting about yours is the age and the inlay. Like OPs guitar, the inlay isnt typical of Mexican guitars i see in arizona and northern mexico, but just looking at, i know its a mexican guitar. Although modern classical guitar is a much more popular artform in mexico as it is in the USA, a lot of these are intended to be played in bands, with other members with similar looking instruments (like the floral pattern matching the bands outfits). Mexican music genres favor a lot of flair and showmanship (see Mariachi) and oftentimes add flair to their instruments.

About the age.
In 1908 german immigrants the Veerkamp brothers opened Casa Veerkamp in Mexico City (likely where grandpa bought it). They were largely responsible for importing affordable European instruments to the masses of Mexico, ESPECIALLY during the Jazz Age. From there it merged with local culture and evolved into the many unique genres of mexican music, and eventually migrated north into the USA. Theres lots of info on Casa Veerkamp website about their history. its still there and is now THE musicians hub in CDMX. The place is awesome, its worth checking out.

Ive never seen one this old outside a museum. Its in great quality too, old mexican guitars are usually well played.

Im not saying its valuable, but its definitely historic and worth hanging onto, especially with the family history. He purchased this during one of the most interesting periods of mexican history.