Newer high quality digital scales define values to a tenth of a pound. Weigh a brand new VRB, then weigh it again when it goes bad. If it has lost so much as a tenth of a pound or 35 grams, your bad....Just make sure you also have a non-volatile check weight to ensure the scale accuracy had not drifted. A bag with 62 pounds of rocks makes a decent counterweight for some GC batteries.
Regular VRB users really should do this weight verification test to determine if written rote agrees with reality. You'd be surprised.