To go one step further, what probably happened here is that when the mechanical movement broke down, your mother took it in to be fixed and was told the following by the jeweler:
"Well ma'am, we can fix the watch, but it will cost a hundred dollars or so. Instead, we can put in a modern quartz movement. It will keep much better time that way and will cost less too."
And so your mother's watch movement went to the great horological graveyard in the sky...
gatorcpa