It's the Circlet of Life (L)

At 10 allowances a run, this leve's 593,380 EXP works out to 59,338 EXP per allowance, which places it 3rd of the 3 Lv 58 Goldsmith Grand Company leves that record EXP. The best of them, The Lovely Hands of Haillenarte (L), returns 235,244 EXP for the same allowance, 296% more.

Across that rung the return runs from 59,338 EXP to 235,244 EXP per allowance — 3 distinct figures spanning 296%, so the wrong pick leaves 175,906 EXP of the allowance unspent.

Nothing above Lv 58 is recorded for Goldsmith Grand Company leves, so this rung is the ceiling at 235,244 EXP per allowance — 31% more than the Lv 56 rung below it.

At Lv 58 this data holds 54 leves paying EXP across 3 categories: the 27 Grand Company ones average 228,371 EXP per allowance, the 3 Fieldcraft ones 1,079,567 EXP and the 24 Tradecraft ones 443,090 EXP, which puts this leve 74% below its own category's average.

Aurum Regis Circlet of Healing ×1 is a Lv 60 Goldsmith recipe, 3 steps deep through 6 intermediates, costing 37 units of raw material and 33 crystals.

Handing that in returns 16,037 EXP and 42 gil for every unit of raw material the order swallows, and the tree needs Alchemist, Goldsmith and Weaver.

The record carries a repeats value of 5. This site reads that as 5 further turn-ins on the same leve — an assumption, because the source data defines no meaning for the field — which would put the ceiling at 3,560,280 EXP and 9,360 gil for the 10 allowances it costs, or 356,028 EXP per allowance.