TIL if you have a bonus item in your storage it will not give you a new one
This is not true. Not Serrated Shield in his inventory it should be created. The others are already there, so they won't be duplicated.
Example after using /bonus, then destroying the shield and reusing /bonus:
Dunno what to tell you, taking the Serrated out of my storage and destroying it was what made /bonus give me another one.
And if I try to recreate it by putting the shield in storage, it still won't give me a new one. I guess the game considers the storage chest as "you already have one.", which would make sense.