I very much doubt the Finns etc in Rio are being weighed by the local authority, nor indeed any dinghies/RC/ yachts in this country. If you are serious about rule inforcement, then do it properly. Sounds like your weights are indeed reliable though!
No-it is more surprising that any authority fronts up with uncalibrated balances. I've seen this many times at dinghy events. Are no measurers scientists? At the very least, a certificate of calibration to ISO17025 for the balance should be pinned up for all to see. Should cost no more than a couple of hundred pounds