Going with a refresher.

Sales

Sale 1: Sold for 24 keys

https://backpack.tf/profiles/76561198192602363#!/compare/1602115200/1602201600

https://backpack.tf/profiles/76561198029897880#!/compare/1602115200/1602115200

Sale 2: Sold to backpack buyer

https://backpack.tf/profiles/76561198074310852#!/compare/1587513600/1601856000

https://backpack.tf/profiles/76561199037317509#!/compare/1599436800/1601424000

Sale 3: Traced 2 keys

https://backpack.tf/profiles/76561198313756528#!/compare/1601337600/1601683200

https://backpack.tf/profiles/76561198260833001#!/compare/1601164800/1601337600

Incomplete sale.

Sale 4: Untrace

https://backpack.tf/profiles/76561198415159702#!/compare/1601078400/1601164800

https://backpack.tf/profiles/76561198313756528#!/compare/1601078400/1601164800

Sale 5: Sold for 12 keys, 20 refined

https://backpack.tf/profiles/76561198119629072#!/compare/1600819200/1600905600

https://backpack.tf/profiles/76561198415159702#!/compare/1600732800/1600819200

This sale rounds down to 12 keys.

Sale 6: Sold for 16 keys, 20.77 refined

https://backpack.tf/profiles/76561198111298748#!/compare/1600041600/1600560000

https://backpack.tf/profiles/76561198119629072#!/compare/1599955200/1600128000

This sale rounds down to 16 keys.

Sale 7: Untrace

https://backpack.tf/profiles/76561198195933333#!/compare/1599350400/1599436800

https://backpack.tf/profiles/76561198111298748#!/compare/1599177600/1599350400

Sale 8: Untrace, but it was to a buyorder I am sure.

https://backpack.tf/profiles/76561198027302727#!/compare/1599350400/1599436800

https://backpack.tf/profiles/76561198195933333#!/compare/1599264000/1599350400

Marketplace sales

https://marketplace.tf/items/tf2/30128;5;u29

Nothing recent.

Current Classifieds

https://backpack.tf/classifieds?item=Belgian%20Detective&quality=5&tradable=1&craftable=1&australium=-1&particle=29&killstreak_tier=0

https://gyazo.com/c3321d0a5ef4311940b1661e60065d28

Summary

Sales at 12, 16, and 24.

Conclusion

Buyers are up to about 18~, excluding 12 and 16 as low outliers.

Going with 24 here.

Take it easy.