I just managed to sell this unusual on SCM.

https://imgur.com/a/oQQmzFd Imgur album of sale, both recorded on SCM and seller's side, and proof of effect (JUL 31 9AM)

https://steamcommunity.com/market/listings/440/Mann%20Co.%20Supply%20Crate%20Key Supply crate key cost at roughly the same time (JUL 31 9AM) was $2.18.

125.01/2.18=57.344, rounded down to 57 keys.

If there's any sales I missed or any miscalculations, please let me know and I'll attempt to correct.