Turtleshell Choker is an accessory in Final Fantasy XII that makes the wearer to cast magicks with gil, rather than with MP. It is a good accessory to magick-users especially in long battles, or when enemies or the battlefield sap the combatants of MP, as long as the party has the gil to spare. The gil required to use it was greatly reduced for the Zodiac versions, where it also bestows small boosts to the wearer's Magick Power and Speed.
Obtain
Original
In the original PlayStation 2 versions, Turtleshell Choker is bought for 9,300 gil from Bhujerba's Street Vendor after the events at Draklor Laboratory. It is also a treasure in Barheim Passage's East-West Bypass (furthest treasure chest in the dead-end bit; 50% chance to appear, 75% chance for gil, 50% chance the item treasure is a Turtleshell Choker without the Diamond Armlet 
), and a rare steal from Emeralditan.
It is made in the bazaar in the "Shell-worked Collar" set by selling two Bomb Shells (obtain from Bomb-type enemies) and two Four-leaf Clovers (obtain from Mandragora Prince).
Despite the equipment's name, and the name and description ("The clasp of this necklace is fashioned from tortoiseshell. For those with discriminating taste.") of its bazaar entry, making it requires no shell loot dropped by tortoise-type enemies (Turtle Shell, Aged Turtle Shell, or Ancient Turtle Shell).
Zodiac
In the updated Zodiac versions, the Turtleshell Choker can't be bought from shops, but sells for 4,000 gil. It is found in a treasure in Nam-Yensa Sandsea's Withering Shores (always appears), Mosphoran Highwaste's Babbling Vale (always appears), and Subterra's Umbra - North (70% chance to appear, 80% chance for gil, 50% chance the item treasure is a Turtleshell Choker without the Diamond Armlet), as well as the Trial Mode stages 88 and 97 with the Diamond Armlet equipped.
It is still a rare steal from Emeralditan and now also the common steal from Gil Snapper in Trial Mode Stage 30.
It is still made in the bazaar in the "Shell-worked Collar" set with the same items as before, and is now also a possible reward in the Hunt Club quest by giving 5 Rare Game trophies to Atak and Blok, and 12 trophies to Stok.
Use
Turtleshell Choker is a great accessory for a heavy magick-user to assure they never have to pause casting due to lack of MP, as long as the party has the gil to spare. The formula for gil-use depends on version, truncated to the nearest 10s place. In the original PlayStation 2 version, it is 50 x (MP x 1.28). E.g. casting Cure (8 MP) costs 510 gil. In the Zodiac versions, it is 10 x (MP x 1.28); e.g. casting Cure (8 MP) costs 100 gil.
Near endgame, the party likely has more gil than they have a need for, making using Turtleshell Choker more viable, especially in the Zodiac versions where using it costs much less. In the Zodiac versions, the characters who have finished their License Board(s) can also equip Cat-ear Hoods to convert their LP-gains into gil, giving the player a constant source of gil without needing to stop in towns to sell loot. (See also: gil grinding)
Turtleshell Choker is good for battles against Rafflesia and entites who sap the party of MP, forcing any magick-users who have Charge or Ether-use as active gambits to just use these over and over. It is also good against long or tough battles, such as against Yiazmat and Omega Mark XII, so the caster never needs to pause to replenish MP. In the Zodiac versions, Turtleshell Choker is also good for the Trial Mode, especially when there is a long gauntlet of entite-type stages who use Fear to sap the party of MP.
Gil costs
| Spell | MP (OG/ZDC) |
Original gil | Zodiac gil |
|---|---|---|---|
| Cure | 8 | 510 | 100 |
| Cura | 36/26 | 2300 | 330 |
| Curaga | 28/24 | 1790 | 300 |
| Curaja | 68/58 | 4350 | 740 |
| Renew | 98/72 | 6270 | 920 |
| Raise | 22/20 | 1400 | 250 |
| Arise | 50/52 | 3200 | 660 |
| Esuna | 24 | 1530 | 300 |
| Esunaga | 72/66 | 4600 | 840 |
| Blindna | 8/6 | 510 | 70 |
| Vox | 8 | 510 | 100 |
| Poisona | 8 | 510 | 100 |
| Stona | 12 | 760 | 150 |
| Cleanse | 20 | 1280 | 250 |
| Dispel | 16 | 1020 | 200 |
| Dispelga | 36/32 | 2300 | 400 |
| Protect | 8 | 510 | 100 |
| Protectga | 36 | 2300 | 460 |
| Shell | 8 | 510 | 100 |
| Shellga | 40 | 2560 | 510 |
| Bravery | 24 | 1530 | 300 |
| Faith | 24 | 1530 | 300 |
| Regen | 16 | 1020 | 200 |
| Confuse | 10 | 640 | 120 |
| Holy | 60/48 | 3840 | 610 |
| Fire | 8/6 | 510 | 70 |
| Fira | 18/16 | 1150 | 200 |
| Firaga | 42/38 | 2680 | 480 |
| Thunder | 8 | 510 | 100 |
| Thundara | 18 | 1150 | 230 |
| Thundaga | 42/40 | 2680 | 510 |
| Blizzard | 8/10 | 510 | 120 |
| Blizzara | 18/20 | 1150 | 250 |
| Blizzaga | 42 | 2680 | 530 |
| Aero | 16/14 | 1020 | 170 |
| Aeroga | 38 | 2430 | 480 |
| Water/Aqua | 12 | 760 | 150 |
| Bio | 24 | 1530 | 300 |
| Shock | 34 | 2170 | 430 |
| Scourge | 48 | 3070 | 610 |
| Flare | 48/46 | 3070 | 580 |
| Scathe | 70 | 4480 | 890 |
| Blind | 10 | 640 | 120 |
| Blindga | 20 | 1280 | 250 |
| Silence | 8 | 510 | 100 |
| Silencega | 22 | 1400 | 280 |
| Sleep | 10 | 640 | 120 |
| Sleepga | 26/22 | 1660 | 80 |
| Poison | 10/8 | 640 | 100 |
| Toxify | 26 | 1660 | 330 |
| Haste | 20/18 | 1280 | 230 |
| Hastega | 70 | 4480 | 890 |
| Slow | 8 | 510 | 100 |
| Slowga | 24 | 1530 | 300 |
| Stop | 20 | 1280 | 250 |
| Immobilize | 16/14 | 1050 | 170 |
| Disable | 16/14 | 1020 | 170 |
| Bleed | 12 | 760 | 150 |
| Break | 14 | 890 | 170 |
| Countdown | 8 | 510 | 100 |
| Berserk | 10 | 640 | 120 |
| Float | 20/16 | 1280 | 200 |
| Vanish | 24/12 | 1530 | 150 |
| Vanishga | 60/24 | 3840 | 300 |
| Reflect | 12 | 760 | 150 |
| Reflectga | 24 | 1530 | 300 |
| Balance | 18 | 1150 | 230 |
| Warp | 18 | 1150 | 230 |
| Gravity | 20/12 | 1280 | 150 |
| Graviga | 36/28 | 2300 | 350 |
| Oil | 8 | 510 | 100 |
| Reverse | 50/20 | 3200 | 250 |
| Decoy | 10 | 640 | 120 |
| Drain | 18 | 1150 | 230 |
| Syphon | 2 | 128 | 25 |
| Bubble | 30/32 | 1920 | 400 |
| Dark | 10 | 640 | 120 |
| Darkra | 20/24 | 1280 | 300 |
| Darkga | 30/38 | 1920 | 480 |
| Death | 30/20 | 1920 | 250 |
| Ardor | 60 | 3840 | 760 |