Did a little scientific research and have hopefully determined a good method for identifying a Chinese VS Korean Unlimited Base set energy card.
It is extremely difficult to tell the two apart at first glance.
I personally pulled both of these cards from a pack and a deck. Under analysis there are slight differences in the card copyright layout, otherwise they are extremely similar in appearance.
It appears Korean will have the Copyright symbol much closer to the artist attribution. Chinese will appear to have essentially a double space, and Korean a single space.
I did some quick analysis. Under black light, the Korean Pokemon text on the back appears to glow brighter than all others, except Australia which is extremely vibrant.
The Chinese front glows brighter than the Korean front. But it is somewhere in between Australia and UK, nowhere near how bright the USA front glows.
It appears like only Australia and Chinese have the excess space between copyright and illustrator text.
Other than USA front / Australia back, it’s pretty difficult to identify any one of the 5 individually without comparing to known examples.