The China mint made 750 individually numbered sets from Shenzhen Guobao with letters of authenticity showing 1st of 750 issued which were used for the NGC label. http://www.govmint.com/2017-china-gold-panda-ngc-ms70-first-day-of-issue-prestige-5-pc-set.html
However, not all of those 750 sets were graded as MS70 by NGC.
Of the 5 denominations the 30g is the rarest...
Only 548 G500Y pieces were graded as NGC MS70: https://www.ngccoin.com/census/world/china-panda-series/sc-367/g500y/varieties/413224/
Only 575 G200Y pieces were graded NGC MS70:https://www.ngccoin.com/census/world/china-panda-series/sc-367/g200y/varieties/413220/
There were more than 750 pieces of G100Y, G50Y, and G10Y graded by NGC so there must have been an additional metric or certificate used for those coins.
The first coins struck at a mint typically have the best details and fewest imperfections.
Though Chinese modern coins have improved their quality control since 1982 it is still interesting to think about having the first struck specimens documented and appraised.
This is initially why designations such as "First Strike' changed to "First Release" or "Early Release," or "First Day of Issue.:
Without the paperwork you can't prove if a coin was actually struck first, only that it was obtained and graded within a certain window, whether it be a day or a month.
With China Gold Corp. certifying a batch of coins as being the first off the coin press, these pieces are given a special designation and are actual "First Strikes."