Bubbling Belgian Detective

New price: 12-13 keys

[proof below]

SALE #1 = invalid

https://marketplace.tf/items/30128;5;u34

Quicksold for 7 keys on marketplace.tf

SALE #2 = 12 keys

https://backpack.tf/profiles/76561198091502579#!/compare/1516233600/1516320000

https://i.imgur.com/peyERuu.png

https://i.imgur.com/zEIvVH8.png

Sold along 2 keys for a Circling Peace Sign Engineer’s Cap (14) = 12 keys.

SALE #3 = invalid

https://backpack.tf/profiles/76561198430662188#!/compare/1515801600/1515888000

Bulk.

SALE #4 = 13 keys

https://backpack.tf/profiles/76561198091502579#!/compare/1516320000/1516406400

https://gyazo.com/23ef5f4087b9175eb5eb498776acd7a8

http://www.tf2outpost.com/trade/29524842 - B/O 13 keys

Sold for 13 keys.

SALE #5 = invalid

https://backpack.tf/profiles/76561198320405152#!/compare/1513209600/1513382400

Better used there.

SUMMARY

Sales: 12 / 13 keys

Sellers: 15 keys (marketplace.tf)

Going with 12-13 keys.