Here are the XEV results.
T61p:
keycode 121 = (keysym 0x1008ff12, XF86AudioMute), state = 0x0 keycode 121 = (keysym 0x1008ff12, XF86AudioMute), state = 0x0 keycode 122 = (keysym 0x1008ff11, XF86AudioLowerVolume), state = 0x0 keycode 122 = (keysym 0x1008ff11, XF86AudioLowerVolume), state = 0x0 keycode 123 = (keysym 0x1008ff13, XF86AudioRaiseVolume), state = 0x0 keycode 123 = (keysym 0x1008ff13, XF86AudioRaiseVolume), state = 0x0
121 = mute, 122 = vol down, 123 = vol up
----
T500
keycode 36 = (keysym 0xff0d, Return), state = 0x10 keycode 122 = (keysym 0x1008ff11, XF86AudioLowerVolume), state = 0x10 keycode 122 = (keysym 0x1008ff11, XF86AudioLowerVolume), state = 0x10 keycode 123 = (keysym 0x1008ff13, XF86AudioRaiseVolume), state = 0x10 keycode 123 = (keysym 0x1008ff13, XF86AudioRaiseVolume), state = 0x10
36 = mute, 122 = vol down, 123 = vol up
Here are the XEV results.
T61p:
keycode 121 = (keysym 0x1008ff12, XF86AudioMute), state = 0x0 olume), state = 0x0 olume), state = 0x0 olume), state = 0x0 olume), state = 0x0
keycode 121 = (keysym 0x1008ff12, XF86AudioMute), state = 0x0
keycode 122 = (keysym 0x1008ff11, XF86AudioLowerV
keycode 122 = (keysym 0x1008ff11, XF86AudioLowerV
keycode 123 = (keysym 0x1008ff13, XF86AudioRaiseV
keycode 123 = (keysym 0x1008ff13, XF86AudioRaiseV
121 = mute, 122 = vol down, 123 = vol up
----
T500
keycode 36 = (keysym 0xff0d, Return), state = 0x10 olume), state = 0x10 olume), state = 0x10 olume), state = 0x10 olume), state = 0x10
keycode 122 = (keysym 0x1008ff11, XF86AudioLowerV
keycode 122 = (keysym 0x1008ff11, XF86AudioLowerV
keycode 123 = (keysym 0x1008ff13, XF86AudioRaiseV
keycode 123 = (keysym 0x1008ff13, XF86AudioRaiseV
36 = mute, 122 = vol down, 123 = vol up