Hey Shep,
Congrats on the copy of SSWS 6. Because Pedrin's guide listed that book as "extremely rare", I bought every copy I ever stumbled upon, unless the price was ridiculous. I ended up with 7 copies.
I did the same with G. I. Combat #87, and I ended up with 21 copies. I did the same with SSWS 151 and I ended up with about 35 copies.
Is SSWS 6 "extremely rare"? I doubt it. Tough to find? Yes. I don't have a copy anymore and I other than my last copy that I sold in 2010, I don't think I've seen another one in 2010 or 2011 so far. It is tough.
Andy