Hi, Casey,
That's actually not a "1735" as the 1735 refers to a specific model in the Blancpain line. That is what is known as a "complete calendar moonphase" model; again, a great watch. It tells the day/date/month and moonphase, as well as the time.
Sorry to read about the passing of your grandfather, as you write, the watch is priceless as a memento of memories. Wear and own it proudly.
TM