Re-suggest, thanks to K1ing for the help!

Sale 1:

https://backpack.tf/profiles/76561198105071091#!/compare/1523664000/1523750400

https://backpack.tf/profiles/76561198032763715#!/compare/1523664000/1523750400

Sold for 11 keys.

Sale 2:

https://marketplace.tf/items/30839;5;u3006

Sold for 33.33 USD, keys @ 1.98, total is ~16.8 keys

Sale 3:

https://backpack.tf/profiles/76561198305676157#!/compare/1521158400/1521244800

Sold for 8 keys + 21 ref

Sale 4:

https://backpack.tf/profiles/76561198061489334#!/compare/1519689600/1519776000

https://backpack.tf/profiles/76561198170071647#!/compare/1519776000/1519862400

Sold for 3 keys + Pro KS Machina(12) + Pro KS Degreaser(6)

Total is 21 keys

Sale 5:

https://backpack.tf/profiles/76561198085628805#!/compare/1519344000/1519430400

https://backpack.tf/profiles/76561198116954937#!/compare/1519084800/1519430400

Sold for 15 pure

Only traceable sales I can find.

Total sales @:

8.77, 11, 15, 16.8, 21

https://steamcommunity.com/market/listings/440/Unusual%20Taunt%3A%20Didgeridrongo

Lowest listing for ~13 keys (may be different as this is using CAD)

http://www.tf2outpost.com/trade/29606410

B/O of 10 keys

http://www.tf2outpost.com/user/76561198027115407

B/O of 20 keys (Sold in bulk)

Considring buyers up to 8 keys, and current sellers, taking 14 - 21 keys.

K1ng's Part:

26-days unsold at 14 in classies, so this will be high. The sales at 15 and 21 are really old now, and the marketplace one will end up being an outlier most likely.

The sale at 11 is probably the only valid one now, supported by the previous B/O of 10 keys. So I would go with 11 flat.