Jin duly sank a birdie at the 18th when play resumed at 0530 GMT to take his score to six under and confirmed he was the only amateur to survive the halfway cut.
He only had four hours' sleep but Jin Jeong's early rise was well worth it, the South Korean all but ensuring the best amateur title at the British Open and earning an outside chance of the Claret Jug itself.
Jin was up with the dawn chorus today to complete his second round after battering winds had curtailed play yesterday.
He duly sank a birdie at the 18th when play resumed at 0530 GMT to take his score to six under and confirmed he was the only amateur to survive the halfway cut.
The Silver Medal guaranteed so long as he completes 72 holes, he holds a share of third place and goes out at 1520 GMT today with the likes of three-times champion Tiger Woods and world number two Phil Mickelson several groups behind him.
"I only had about four hours'' sleep having finished quite late last night, then got up early this morning to go to the practice ground," the dapper 20-year-old told reporters by the 18th green.
The Australia-based player withstood most of the barrage the weather threw at the players on Friday with four birdies and two bogeys in one of the few rounds to beat par.
He has already shown his love for the Scottish links and Muirfield in particular where last month he became the first Asian to win the British amateur championship since the event's inception 125 years ago.
"It was a nice way to finish with a birdie at the last. I played very well yesterday. Tried to keep it low, even with the driver," he said.
"We often have that sort of conditions where I play in Melbourne."
Now that a second world class amateur accolade has been secured, he said he hoped he could play without pressure and try to reel in leader Louis Oosthuizen, six shots ahead of the South Korean on 12 under.
"My first goal was to take the Silver Medal and it looks like I've achieved that," he said.
"All the pressure has gone so I can enjoy the other two rounds. I will try to catch the leader. He's at 12 under and it is a long way but I'll try to do my best."
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