THE MYSTERY IS SOLVED!
OK, it was my mum's and she bought it from one of them Ann Summers parties. She never wore it though.
Not too long ago my sister, 8, and her friend, 7, were playing dress-up and make-overs, and they'd obviously had a look through my mum's clothes. And my sister's friend put it on and they went downstairs to show off their new look, obviously my mum freaked out in embarrassment and told her to get it off quick, and later on my sister must have put it in my clothes box.
I can see my daughter doing something like that.
You can see your daughter finding your corset?
I can see her taking something of mine for dress-up, like a pair of hot pink high heel shoes I bought to wear to a wedding with a hot pink silk dress, but she has her own green velvet Renaissance dress with a burgundy jacket with very long sleeves, lined with gold satin. Here's the pattern I used to make it for her, View C, but I changed the jacket to have a frog fastener in the front so she could put it on by herself and I beaded the edge of the collar with pearls. That hat with two cones and the veil was also the hat she picked:
Here's the pattern I used to make mine, also View C, but in navy blue velvet: