Well, actually it's not on our tree this year as my wife decorated it and she doesn't like this particular decoration. Of the other two old decorations we have (both metal bells), she only likes one so only that one made it to the tree.
This particular decoration is inherited from my paternal grandfather's sister, whom I always knew as Aunt Irene (although she was actually my great aunt and Irene was her middle name — her first name was Kathleen). She died just before Christmas, so her tree decorations were a reminder of that. To be honest, as I was just a kid at the time, I remembered the time of year she died anyway as she'd already bought us our presents — very considerate of her.
This particular bauble is of a kind they don't really make these days: small, with a very deep, conical concave depression that captures the light and sparkles. I did have some other decorations like that from my parents' decorations, but they're quite fragile and easily shatter when dropped.
OK, I admit it, I was just testing out the zoom on the 8 megapixel camera built into my new phone (and also the Google+ live update service, but in that case less successfully).