Blaze:

https://backpack.tf/profiles/76561198009471724#!/compare/1645315200/1645401600

https://backpack.tf/profiles/76561198044358370#!/compare/1645315200/1645401600 - bulk

https://steamcommunity.com/market/listings/440/Strange%20Coffin%20Nail%20Shotgun%20%28Factory%20New%29

https://steamcommunity.com/market/pricehistory/?country=US&currency=1&appid=440&market_hash_name=Strange%20Coffin%20Nail%20Shotgun%20%28Factory%20New%29 - new sale at 26~ keys

given sales are at 26, 26, 29, 81, 97, 140, it would make more sense to go with 81 - 97 here as 140 looks like an outlier compared to the other sales and it would balance it a bit more

Credits to MetalMalisha:

just sold one for 140 pure https://backpack.tf/profiles/76561198069854269#!/compare/1645142400/1645228800

https://backpack.tf/item/11291309934

Technically some of these histories appear on this version of the item: https://backpack.tf/stats/Strange%20Decorated%20Weapon/Coffin%20Nail%20%7C%20Shotgun%20(Factory%20New)/Tradable/Craftable, but since it is only this variant that has been priced in the past, pricing it here.

https://mannco.store/item/440-strange-coffin-nail-shotgun-factory-new

Nothing

https://marketplace.tf/items/tf2/15132;15;w1;pk76;strange

https://manic.tf/keyprice/?at=2021-12-24&site=marketplace.tf

$175/1.81=~97k

https://steamcommunity.com/market/pricehistory/?country=US&currency=1&appid=440&market_hash_name=Strange%20Coffin%20Nail%20Shotgun%20%28Factory%20New%29

Oct 27, ~80.6k, ~81k

Dec 10, ~25.7k, below buyers

(Note none of the festivized variants have any sales on SCM either)

https://backpack.tf/item/4681727864

https://backpack.tf/profiles/76561198054693888#!/compare/1636502400/1636848000

https://backpack.tf/profiles/76561198053700606#!/compare/1636761600/1636848000

https://steamcommunity.com/market/pricehistory/?country=US&currency=1&appid=440&market_hash_name=Strange%20Professional%20Killstreak%20Coffin%20Nail%20Shotgun%20%28Factory%20New%29

SCM, Nov 14, ~29.3k, below buyers

https://backpack.tf/item/4768692103

https://backpack.tf/profiles/76561198102176850#!/compare/1579478400/1637193600

https://backpack.tf/profiles/76561198056080374#!/compare/1637193600/1637280000

untrace

https://backpack.tf/profiles/76561198056080374#!/compare/1639785600/1639872000

https://backpack.tf/profiles/76561198872480703#!/compare/1640217600/1640304000

I dunno

https://backpack.tf/item/6219227803

https://backpack.tf/profiles/76561198131966769#!/compare/1638662400/1639008000

https://backpack.tf/profiles/76561198109756155#!/compare/1638921600/1639008000

SCM, not sure which, appears as basic KS which has no recorded sales https://steamcommunity.com/market/pricehistory/?country=US&currency=1&appid=440&market_hash_name=Strange%20Killstreak%20Coffin%20Nail%20Shotgun%20%28Factory%20New%291

https://backpack.tf/item/10850553411

https://backpack.tf/profiles/76561198052431073#!/compare/1635206400/1635292800

https://backpack.tf/profiles/76561198119509036#!/compare/1635206400/1635292800

Trade-ups I presume

81-97 as Blaze suggested.