Sold for $299 on SCM:

http://i.gyazo.com/b479c2a90b0f53d4af54f7b366355820.png

http://backpack.tf/profiles/76561198044423356?time=1431154800 (May 9th)

http://backpack.tf/profiles/76561198044423356?time=1431241200 (May 10th)

299 / 2.5 / 1.15 = 104.0 keys

299 / 2.5 = 119.6 keys

~100 - 120 keys

I've confirmed with seller on this sale but forgot to screenshot. Shouldn't matter as there is only 1 sale on May 10th.

http://steamcommunity.com/market/listings/440/Unusual%20Virtual%20Viewfinder

Sold for Stare From Beyond Deep Cover Operator (200) + Professional Killstreak Loose Cannon Kit (4):

http://www.tf2outpost.com/trade/25749247

http://backpack.tf/profiles/76561198123066949?time=1429599600 (April 21st)

http://backpack.tf/profiles/76561198123066949?time=1429772400 (April 23rd)

Stare From Beyond Deep Cover Operator came from here:

http://backpack.tf/profiles/76561198071581206?time=1429686000 (April 22nd)

http://backpack.tf/profiles/76561198071581206?time=1429772400 (April 23rd)

Buyout of 165 keys

Bulk sale for Disco Beat Down Virtual Viewfinder:

http://backpack.tf/profiles/76561198067465104?time=1429426800 (April 19th)

http://backpack.tf/profiles/76561198067465104?time=1429599600 (April 21st)

Sold for duped Burning Flames Noble Amassment of Hats (~110):

http://backpack.tf/profiles/76561197991783701?time=1426834800 (March 20th)

http://backpack.tf/profiles/76561197991783701?time=1426921200 (March 21st)

~110 keys

Sold for It's A Secret To Everybody Private Eye (90) + Orbiting Fire Samur-Eye (22) + ~9 keys in items:

http://backpack.tf/profiles/76561198095259560?time=1428735600 (April 11th)

http://backpack.tf/profiles/76561198095259560?time=1428822000 (April 12th)

(90 + 22 + 9) * .9 = 108.9 keys

~110 keys

Sold for Chiroptera Venenata Well-Rounded Rifleman (100) + Memory Leak Pure Tin Capotain (18) + 15 keys:

http://backpack.tf/profiles/76561198050824312?time=1428476400 (April 8th)

http://backpack.tf/profiles/76561198050824312?time=1428562800 (April 9th)

(100 + 18) * .9 + 15 = 121.2 keys

~120 keys

Sold with ~6 keys in items for Circling Peace Sign Hong Kong Cone (240):

http://backpack.tf/profiles/76561198042664154?time=1427958000 (April 2nd)

http://backpack.tf/profiles/76561198042664154?time=1428476400 (April 8th)

~230 keys. Outlier.

Sold for Dead Presidents Hong Kong Cone (75) + 6 buds (10) + 4 keys:

http://backpack.tf/profiles/76561198042664154?time=1426834800 (March 20th)

http://backpack.tf/profiles/76561198042664154?time=1426921200 (March 21st)

75 * .9 + 60 + 4 = 131.5 keys

~130 keys

Sold with 8 keys for Scorching Flames Brigade Helm (130):

http://backpack.tf/profiles/76561198056793885?time=1426748400 (March 19th)

http://backpack.tf/profiles/76561198056793885?time=1426834800 (March 20th)

130 - 8 = 122 keys

Presumably offered. ~120 keys

Sales at 100 - 120, ~110, ~110, ~120, ~120, ~130, ~165, ~230

Going with 100 keys - 130 keys.

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Professional Killstreak Loose Cannon Kit:

Orbiting Fire Samur-Eye and Memory Leak Pure Tin Capotain are both outdated, but their respective sales should fall in range regardless.