Very cool to have the inner and outer boxes and it looks to be in great shape. Lovely memory of your grandmother and quite a fancy watch obviously, really a legitimate piece of jewelry. I'm not familiar with the case-maker's mark, but I'm sure someone else will immediately recognize it and give you some information about the origin. Where are you located BTW, what country? The serial number on the movement is the key to dating it but it's too blurry for me to read. Could you perhaps type it in, at least the first few digits?