There's an extra "s" in the item description. :)

0xabcdef 22 Feb 2018:

Looks like a mod (non-vanilla) item

assumedpseudonym 22 Feb 2018:

 Yep, that’s from SM&M++. (…I still remember suggesting the name for that when Shrike pitched the item description, heh…)

derakon 22 Feb 2018:

Oh, my bad! I thought it was vanilla.