Damn I hadn't noticed that before. Looks like mine was probable the 515. It definatly had the SAT/MD, and the Cable button. But the reciever doesn't say TX-SR601 on it it says TX-SR600. And I probably bought it around 2002 and 2003 time frame.
If the 601 came out around 2003 like you say, than they probably had a 600 and it is most likely the same remote.
Its only around $60 and it does look identical, mine as well try it.
Thanks for the comparison, I was always looking at the small non blown up pictures.