Complex sentence: Alternatively, balls are usually pre-marked with the brand and model of golf ball, and a letter, number or symbol that can usually (not not always) distinguish a player's ball from other balls in play and from lost or abandoned balls on the course.
Split into simpler sentences: Alternatively, balls are usually pre-marked with the brand and model of golf ball, and a letter, number or symbol. This combination can usually (not not always) be used to distinguish a player's ball from other balls in play and from lost or abandoned balls on the course.