Tier 4 Materia rate?

[Highlanderx]

Just to add to this

1/15 For Electrum Choker(ilv49) since 2.0 on Tier IV

Useless to add, since from 2.0 until 2.1, only ilevel 55+ items could turn into Tier IVs.
From 2.0 to 2.1 converts were
Tier I = ilevel 1-29
Tier II = ilevel 30-44
Tier III = ilevel 45+
Tier IV = a small chance at ilevel 55+, ilevel 70 for garunteed(though just read about this, never converted ilevel 70s myself)


After 2.1 It seems any of the ilevel ranges has a small chance of converting to the next higher Tier materia.