There are sales at 12 and even 15. You will need to check out the other sales too.

You need to list out all of the mp sales in order preferably and use either manual calculation or manic's scipt (See here: https://github.com/mninc/keyprice-links) for working out the price in keys of the sales.

I'll give you a hand with the mp sales:

https://marketplace.tf/items/tf2/31101;5;u144

Taking last 2 months, lots of sales to use

From 29/05/20 onwards

May 29th - $21 / $1.94 = 10.82 keys

May 30th - $23 / $1.94 = 11.86 keys

May 31st - $27.44 / $1.91 = 14.37 keys

June 12th - $30 / $2.00 = 15.00 keys

June 29th - $21 / $2.01 = 10.45 keys

July 10th - $18.2 / $2.00 = 9.10 keys

July 12th - $20.79 / $1.98 = 10.50 keys

July 15th - $19.99 / $1.99 = 10.05 keys

July 17th - $19.5 / $1.97 = 9.90 keys

July 19th - $19.5 / $1.97 = 9.90 keys

July 25th - $20.59 / $1.93 = 10.67 keys

July 27th - $23 / $1.92 = 11.98 keys

You will also have to check through buyouts for these mp sales as they will cap if the buyout is lower than the sale

Here are histories that you will need to check for other sales to:

https://backpack.tf/item/8914353273

https://backpack.tf/item/8712998996

https://backpack.tf/item/8682843502

https://backpack.tf/item/8668033972

https://backpack.tf/item/8336872791

https://backpack.tf/item/8495945708

https://backpack.tf/item/8389853475

https://backpack.tf/item/8383142708

https://backpack.tf/item/8347446541

Feel free to add me for anymore help or join the discord here https://discord.gg/f5VS7cr for help in #suggestion-discussion