I can find one that exists, history found here: https://backpack.tf/item/9450267613

My bot sold for 12.5 keys on 04/02/21 to someone that seems to be accruing unusual King Cardbeards: https://backpack.tf/profiles/76561198207541888

Quick sold to the bot for 9k34 ref on 28/01/21

Gladiator stats shows a sold price for 14 keys on the 21/01/21 move from Protein Shake bot to Chicken Burgers (cannot confirm through backpack compare)

Screens for those found here: https://imgur.com/a/xj0XIgN

I can't trace any of the other moves. Ignoring the 9k34 as a quicksale dump, rounding the lower end to 12 keys and giving 14 keys as the top end of the suggested range.