Un-Knowingly selling or Assimilating

[Roth_Trailfinder]

The solution, actually, is to stop using the Actions & Traits -> Materia Assimulating (or Desynthesis).

Instead, go directly in your inventory/Armoury Chest to the item you want to convert/desynth. Select the item (move cursor over it and press Square; don't know keyboard/mouse controls) and from the list that comes up, choose to either Convert (to materia) or Desynthesis.

The problem with the two menu items I'm saying to avoid is they do not tell you what is being used in an Equipment Set. If you go directly to the Hands section of the Armoury Chest (for example) you will see whether or not the item is part of a saved Equipment Set because pieces in saved Equipment Sets have that little notepad icon in the lower right corner.

As for selling ... that's a bit harder. Sorry Caoihmin, but if its one of a bunch of pieces you're storing for Spiritbinding (and then conversion into Materia) you will have to keep track of that yourself. If you've got four Woolen Smocks saved for eventual SB'ing, but only one Equipment Set, the other three won't show that icon in your inventory/Armoury Chest. The only thing you can do is keep track of the replacements for your current Spiritbinding Equipment Set yourself.