@ricci Close enough. I think it might have been a 5509. This an old picture from a lab I ran, and being from around 2002, I don't think I would have had a 6509 to play around with, they were too valuable to us at the time. But I could be wrong.
Another picture of it here. Is that a 6509 or 5509? I can't tell by looking anymore, been awhile since I've touched either.