Sold:

https://marketplace.tf/items/99;5;u35 - sold for $37.99 = 19 keys

https://backpack.tf/profiles/76561198061717026#!/compare/1494547200/1494720000 - sold for Smoking Company Man (18) = 18 keys

https://backpack.tf/profiles/76561198254212752#!/compare/1491523200/1491609600 - bulk

https://backpack.tf/profiles/76561198304138933#!/compare/1496188800/1496275200

https://backpack.tf/profiles/76561198099785339#!/compare/1496188800/1496275200 - ?

https://backpack.tf/profiles/76561198130218451#!/compare/1494028800/1494115200 - sold with 1 key for Orbiting Fire Chieftain's Challenge (19) = 18 keys

https://backpack.tf/profiles/76561198166763739#!/compare/1493942400/1494028800 - sold for Strange Professional Killstreak Frying Pan (10) + 8 keys = 18 keys

https://backpack.tf/profiles/76561198000610763#!/compare/1491436800/1491523200 - ?

https://backpack.tf/profiles/76561198204824055#!/compare/1491436800/1491523200 - sold for 7 keys + sweets (1) = 8 keys (quicksold)

https://backpack.tf/profiles/76561198204824055#!/compare/1491177600/1491264000 - bulk

https://backpack.tf/profiles/76561198002757046#!/compare/1491177600/1491264000 - bulk

https://backpack.tf/profiles/76561198304138933#!/compare/1497052800/1497139200

https://backpack.tf/profiles/76561198049618390#!/compare/1496880000/1497225600 - ?

Conclusion:

sales at 8, 18, 18, 18, 19

taking 18-19 keys