Just a quick update before I go to bed - I found the box. I don’t have a translation for it yet (yandex and google failed me 
).
While I was looking for it, I also came across the case for the first release from 1997.
I also found a Meiji product list from Autumn of 1997. Which seems to be when the first series of snacks containing the pokemon cards launched.
Red writing:
新製品 New product
Writing down the side:
部地区発売 For sale is some regions
So it seems the series started around September 1997, otherwise it wouldn’t likely have been listed as a new product, nor feature the first box of the series. Admittedly, It’s not a release date - but it’s something.
For those of you committed enough to still be reading this, you might find the savoury biscuit snack on the back interesting also.
