I really appreciate all of the feedback. I've spent some more time working to understand the parameters controlling an AU vs. BU Jefferson and I must say I think it's easier to make the determination with LMC's/LWC's!
Points of confusion: 1) Making the determination between poor strike and wear on high spots. I've looked at some uncirculated coins from mint sets that exhibit what appears to be wear (but probably isn't) and have done some comparisons. Also noticing some nickels from mint sets don't appear to have any mint luster at all or exhibit breaks in luster.
2) How dings/marks affect AU/BU designation. I didn't think coin dings/marks affected uncirculated status in that these can happen in bags. Confused a bit on this.
3) Identifying wear on toned coins.
Would love to hear thoughts. Just trying to get my arms around this whole nickel grading thing.