the only way to tell is by the number stamped on the side of them...here is the gibson pot guide...
44071079 - long shaft "tone" pot, 100K audio in very late 70s through mid 1980s, 500K audio in 1990s up until today
44070034 - long shaft "volume" pot, 300K linear
44070028 - short shaft "volume" pot, 300K linear
44070035 - short shaft "tone" pot, 500K audio
44070500 - short shaft pots, 500K, used in recent Historics, the pots with the scary plastic insides
-Mike