Got clarification from the seller - it was through an app called Swish that seems like it's PayPal for Swedes. With little activity on the Forums, we'll consider it equivalent to PayPal for the sake of the Key price with a few threads from years ago treating them equally.

As for the Key mini at the time:

https://forums.backpack.tf/topic/84136-%E2%9C%A8-%E2%96%88%E2%96%93%E2%96%92%E2%96%92%E2%96%91%E2%96%91%E2%96%91%F0%9F%9F%A2-%F0%9D%90%92%F0%9D%90%9A%F0%9D%90%9F%F0%9D%90%9E%F0%9D%90%AD%F0%9D%90%B2-%F0%9D%90%9F%F0%9D%90%A2%F0%9D%90%AB%F0%9D%90%AC%F0%9D%90%AD-%F0%9F%92%B8-210-%F0%9D%90%93%F0%9D%90%AB%F0%9D%90%AE%F0%9D%90%AC%F0%9D%90%AD%F0%9D%90%AC-%F0%9F%92%AF-fiky-is-buying-backpacks-b-tf2-keys-172-paypal-%E2%96%91%E2%96%91%E2%96%91%E2%96%92%E2%96%92%E2%96%93%E2%96%88/ - Successful buyer at $1.76 and $1.78

https://forums.backpack.tf/topic/68510-buying-keys-for-174-backpacks-via-paypal-900-trust-ratings%E2%9C%85/ - Successful buyer at $1.72

https://forums.backpack.tf/topic/82455-buying-tf2-keys-via-paypal-for-175-usd-each/ - Successful buyer at $1.75 and $1.79

https://forums.backpack.tf/topic/78488-%F0%9F%97%9D%EF%B8%8Fbuying-keys-for-172-paypal-166-for-crypto%E2%9C%85-160-trust/ - Successful buyer at $1.78

https://forums.backpack.tf/topic/76871-buying-keys-170-each-buying-backpacks-ref-tools-all-items-paypal-250-trust/ - Successful buyer at $1.70

https://forums.backpack.tf/topic/81019-buying-keys-for-175-and-backpacks-via-paypal-100-trust-and-over-100000-worth-of-transactions/ - Successful buyer at $1.78

https://forums.backpack.tf/topic/86806-buying-tf2-keys-%F0%9F%94%91-174-paypal-%F0%9F%94%91-50-trust-ratings-%E2%9C%85/ - Unsuccessful buyer at $1.73-$1.75

https://forums.backpack.tf/topic/87784-buying-keys-via-paypal-173/ - Successful buyer at $1.75

https://forums.backpack.tf/topic/87796-buying-and-selling-keys-via-paypal-and-wise-%F0%9F%92%B5-b-170-s-182%F0%9F%92%B0-140-trust-reputation-%E2%9C%85/ - Successful buyer at $1.74

https://forums.backpack.tf/topic/88225-%F0%9F%97%9D%EF%B8%8Fbuying-keys-for-176-via-paypal%F0%9F%92%B5/ - Successful buyer at $1.74

https://forums.backpack.tf/topic/87230-%F0%9F%94%91buying-backpacks-unusuals-keys%E2%80%8B%E2%80%8B%E2%80%8B%E2%80%8B%E2%80%8B%E2%80%8B%E2%80%8B%E2%80%8B%E2%80%8B%E2%80%8B%E2%80%8B%E2%80%8B%E2%80%8B%E2%80%8B-174-225-cad-%E2%80%8B%E2%80%8B%E2%80%8B%E2%80%8B%E2%80%8B%E2%80%8B%E2%80%8B%E2%80%8B%E2%80%8B%E2%80%8B%E2%80%8B%E2%80%8B%F0%9F%94%91-selling-keys-182-25-cad%F0%9F%94%91115-trusts%E2%9C%85-wise-crypto-zelle%F0%9F%8D%81e-transfer%F0%9F%8D%81-paypal-alipay125-rmb/ - Buyer at $1.74 (maybe successful?)

https://forums.backpack.tf/topic/84226-buying-keys178backpacksquicksellshigh-tiers-with-paypal/ - Unsuccessful buyer at $1.76-$1.78

https://forums.backpack.tf/topic/85507-%F0%9F%92%B0-%F0%9D%97%95-%F0%9D%97%9E%F0%9D%97%B2%F0%9D%98%86%F0%9D%98%80-%F0%9D%97%95%F0%9D%97%AE%F0%9D%97%B0%F0%9D%97%B8%F0%9D%97%BD%F0%9D%97%AE%F0%9D%97%B0%F0%9D%97%B8%F0%9D%98%80-%F0%9D%97%95%F0%9D%98%82%F0%9D%97%B9%F0%9D%97%B8-%F0%9D%97%9C%F0%9D%98%81%F0%9D%97%B2%F0%9D%97%BA%F0%9D%98%80-%F0%9F%94%91-%F0%9D%97%A3%F0%9D%97%94%F0%9D%97%AC%F0%9D%97%A3%F0%9D%97%94%F0%9D%97%9F-%F0%9D%9F%AD%F0%9D%9F%B3%F0%9D%9F%B1-%C2%B7-%F0%9D%97%96%F0%9D%97%A5%F0%9D%97%AC%F0%9D%97%A3%F0%9D%97%A7%F0%9D%97%A2-%F0%9D%9F%AD%F0%9D%9F%B3%F0%9D%9F%AD-%C2%B7-%F0%9D%97%96%F0%9D%97%94%F0%9D%97%97-%F0%9D%97%98-%F0%9D%97%A7%F0%9D%97%A5%F0%9D%97%94%F0%9D%97%A1%F0%9D%97%A6%F0%9D%97%99%F0%9D%97%98%F0%9D%97%A5-%F0%9D%9F%AE%F0%9D%9F%AF%F0%9D%9F%B0-%F0%9F%8D%81-%E2%9C%85-%F0%9D%9F%B2%F0%9D%9F%B1-%F0%9D%97%A7%F0%9D%97%BF%F0%9D%98%82%F0%9D%98%80%F0%9D%98%81-%F0%9D%97%A5%F0%9D%97%AE%F0%9D%98%81%F0%9D%97%B6%F0%9D%97%BB%F0%9D%97%B4%F0%9D%98%80-%C2%B7-%F0%9D%9F%B1%F0%9D%9F%AC%F0%9D%9F%AC%F0%9D%9F%AC%F0%9D%9F%AC%F0%9D%9F%AC-%F0%9D%97%A7%F0%9D%97%BF%F0%9D%97%AE%F0%9D%97%BB%F0%9D%98%80%F0%9D%97%AE%F0%9D%97%B0%F0%9D%98%81%F0%9D%97%B2%F0%9D%97%B1-%E2%9C%85/ - Unsuccessful buyer at $1.77

https://forums.backpack.tf/topic/80422-buying-tf2-keys-%F0%9F%97%9D%EF%B8%8F178-paypal%F0%9F%97%9D%EF%B8%8F-tod-%F0%9F%8E%9F%EF%B8%8F065%F0%9F%8E%9F%EF%B8%8F-%E2%9C%85highest-buyer-i-pay-fee-%E2%9C%85-i-can-buy-in-euro-%E2%82%AC-70rep-cashout-your-bp-for-money-or-keys/ - Unsuccessful buyer at $1.76

https://forums.backpack.tf/topic/84714-buying-keys-174-each-buying-backpacks-paypal-300-trust%E2%9C%85-200000-usd-transacted/ - Successful seller at $1.76 and $1.78

https://forums.backpack.tf/topic/72542-buying-keys-18-paypal-limited-batch-53225-filled/ - Unsuccessful buyer at $1.80

https://forums.backpack.tf/topic/80407-buying-keys-for-176-usd-tour-of-duty-tickets-for-074-usd-refined-metal-for-001-usd-via-paypal/ - Unsuccessful buyer at $1.76

$1.74 - $1.78 can be taken as a tightened, common range, so that'll make the sale 100 Keys. Seeing as the buyer gambled it, immediately, 100 can be excluded, but it somewhat supports taking 90 Keys with 35 having also been a quicksale.