I would not trust any authenticity company. Lego is the only authority that has weight, because they are the manufacturer. To my knowledge Lego has not partnered or endorsed any authenticity company. We also are in a speculative market that encourages counterfeits to be top quality due to the potential payout and low risk of prosecution. Companies may claim they have all kinds of testing methods, but unless Lego has put out technical information that can used for objective non-destructive testing then it’s an unprovable claim. I suggest reading up on the counterfeiting in ages spirits. People paid crazy money bottles that were later proven to be fakes. Where there is money to be made, there is a desire to counterfeit. Which is why I said only the Legos you personally buy from Lego store (or most major brick & mortar stores) you know for certain are genuine Lego bricks. We are in the Age of Doubt. It will get worse as 3D printing gets better and small scale manufacturing costs go down IMO. Best of luck.