Scales have to be calibrated appropriately and "secret" checkers show up and do a review to make sure you aren't getting cheated by shortweighting something. They also check "freshness" dates. What about rules regulating gun sales? Any oversight/audit of those by any regulatory agency? What about gas station pumps? Aren't they checked to make sure that what the dial shows is actually what is being pumped and that the price shown is actually what is being charged and that the fuel in the well is actually what it is advertised to be? How important is calibrating and checking for accuracy to you?
