Goes to my point about calibration - sounds like your scale is reading 120.20 for some, 120.00 for others, so likely they are different from each other in weight, but without accurately calibrating the scale, there is no reason to believe those numbers are absolute "true" weights, that someone else would also get on their calibrated scale.
But, if you have access to buddy or whomever with a calibrated scale, can make or use your own things as a "calibration weight" - what their scale says it weighs is likely the "true" weight. I had reason to do some dust sampling at work some years ago - draw air through a filter - weigh filter before and then after the sampling - the lab quality Mettler scale had to be sent to NIST for calibration first - I think it went to .0001 grams accuracy, possibly even to the fifth digit - even in very dusty work environment, not much to weigh on a 1" square filter!!!
Lab would weigh and label new filter cassettes - sampling people would use some of those cassettes - different people would receive the used cassettes and also include some never used ones - back to lab - the "blanks" were to discover how correct or how accurate was their ability to weigh things - they did not know which were the same as they weighed before and which may have contaminate on the filter - the blanks needed to be come back with identical weights correct, in order to accept any of other numbers that they reported - else had to reject whole batch and redo whole commotion again. Getting a "number" was useless - had to know it was an "accurate" and "correct" number, that could be replicated, if necessary.
