Thought about putting this in the off topic area, but will keep it among friends. Others welcome to chime in.
We've heard it said, when all else fails you can always trust the weights. They never lie.
I call bullshit.
Find a scale at your gym or house you can trust and weigh your 45s.
If they are off. Calculate the difference of 4, 8, or 10. Weigh the damn bar too along with the rest. The total can be significant.
For example, your 45s are really around 41 to 43. That 500lb pull could be 460.
This can make or break your competition lifts. Assuming your Fed uses top quality equipment.
You would think in this day and age a plate stamped with a number would actually be true.
If there is a difference, at least you'll be aware of the truth.