This plate was called “the holy sign of dedication,” showing that the high priest was set apart to a service of special holiness. (Ex 28:36; 29:6)
... The things made holy by God’s decree included the altar of sacrifice (Ex 29:37), the anointing oil (Ex 30:25), the special incense (Ex 30:35, 37), the garments of the priesthood (Ex 28:2; Le 16:4), the showbread (Ex 25:30; 1Sa 21:4, 6), and all the furniture of the sanctuary.