The Special Charm is an item that greatly increases the chance for daily Luck.
The formula used to calculate daily luck (as of PC v1.11) is:
If player has Special Charm and a random number between 0.0 and 1.0 is less than 0.8 Then Daily Luck = 0.1 Otherwise Daily Luck = a random number between -0.1 and 0.1
Since the Special Charm is unavailable, the last part of the formula always executes.
Obtaining the Special Charm
It is possible to edit a saved game file and add the Special Charm to your wallet. You must find
<hasSpecialCharm>false</hasSpecialCharm> and change it to
With SMAPI and its included "Trainer Mod", the debug command debug specialCharm can be used.