For a dial caliper I use Etalon. Swiss made, and by far the smoothest caliper I've ever used, and I've used them all.
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For a digital caliper, I use Brown & Sharpe Dura Cal. Swiss made also, by Tesa. Also note that the B&S is IP67 compliant for use around fluids. Caliper in imperial mode.
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Caliper in metric mode.
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