Different necklaces: 9
Best one was in FLYF- Silver with a round medallion which had the profile of an Indian with headdress. The headdress had green & black feathers on it.

Out of 96 Ep's Walter was not in:
Innocent;Rescue;Mother;Gambit; Obsessed;Missing & Verdict.
He was in 89 Ep's.

Totally different ones: 10
Explanation: Most were navy blue or dark enough to look black with white print on it.

Exceptions: Red with white/black:
"Walk On By"
"Nikita"

White with purple/aqua/black:
"Love"(Looked Oriental)

Aqua with white/black:
"Noise"

Rose with white/black:
"Last Night","First Mission" & "Not Was"

Green with white/black:
"Soul Sacrifice","Spec Ops" & "Old Habits"

Navy Blue with dots all over:
"Escape","Gray", "Choice"

Multi Colored (tie dyed)
"On Borrowed Time"

Gray with white:
14 Ep's with White in S4

Navy with white:
in S5 (this was different pattern from the rest)

2 Ep's showed him with his hair down-
"Third Person" "
Slipping Into Darkness"

Wore a mans hat 1 time
"Into the Looking Glass".