Thanks for the info, kingdawar! That's about the most beautiful composition I've ever seen; I knew it didn't compose itself! (Pretty sure it wasn't mimma, or he/she would have taken credit.) I thought I'd seen it before, but I didn't remember it and spent more time than I care to admit -- but I solved it! I remember solving it long ago (maybe 10 years ago) as part of the solving ladder (Key Krackers) in Chess Life.