I really like the Iron Mountain series. From an old advertisement I've seen all the Iron Mountain pieces are:
Skillet 3, 4, 5, 6, 7, 8, 9, 10, 12, 14, chicken fryer
Skillet Lids 6, 7, 8, 9, 10, chicken fryer
Round Griddles 8, 9
Long Griddles 7, 8, 9, 10, 11
Dutch Ovens 7, 8, 9, 10
Any skillet lid other than the chicken fryer and maybe the 8 is worth it's weight in gold. Long griddles are hard to find and last I heard no one has given proof of ever actually seeing the 11 but it is in the ad. Dutch ovens other than 8 are hard to find.
From my experience 10 skillets normally go for $75-100 and the 12 somewhere around $200.
If you do some searching you can find the pattern numbers either in the book or someone out there has a compiled list, neither of those are mine so I can't share it here.