Licensed Major League Baseball vendors like Louisville Slugger keep detailed and accurate records. These records date back decades and can be viewed for research purposes. Teams and players place orders that detail the bat’s weight, length, wood type and other characteristics. These can be used to validate if a specific make and model of bat was ever ordered and used by a particular player.
Game-use indicators can include: ball marks, pine tar presence, taping pattern and player markings like uniform number and initials.
If a bat has authentic maker’s marks and the presence of game-use traits, even the most seasoned authenticators can provide only an opinion as to whether the bat has been used in a game. All of this criteria is merely circumstantial evidence. The only way to factually determine actual game usage is a signed and witnessed affidavit from the player and detailed photo-matching of the player using the bat.