I guess you'd start with Starrett pretty much top of the line IMO anyway, made in the USA but they are not cheap! A 6" stainless steel dial caliper will set you back $120 (give or take)... No batteries needed... ever! Their are a lot of high end calipers but I think that kind of money is unnecessary for our purposes.
From there you can pick up an RCBS, Hornady, Lyman, frankfort arsenal, Craftsman or Fowler all of these are around $50 to $25.
Harbor freight offers a pretty good selection of dial & digital calibers for under $20. It pretty much depends on your pocket book and tolerance for changing batteries and perhaps quality becomes an issue at this range. Although they do offer some very inexpensive 6" calipers that work very well - "Cen-Tech" comes to mind.
Stay with the 6", this will handle most anything you will run into.
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