It's the Circlet of Life (L) level 58
Each Turnin of HQ items will grant a reward of 1,501,740 XP and 3,120 Gil. You will make a gil profit if you can obtain the 2 items for less than 1,560 each.
|58 to 59||3,427,200||5||10||1||3||6||1|
|59 to 60||3,888,000||6||12||1||3||6||1|
Because this is a Repeatable Turnin, using one leve allowances will net you 6 turnins, as opposed to 5 allowances allowing only one turnins with other leves.
Most likely you will stop doing this leve after 5 levels, but depending on market prices/etc it may be benefitial to keep turning it in well past that. Also remember to Diversify. The same quest will not always be available to choose.
Use your best judgement when deciding which level to mass produce.