The JCII sticker was a marketing ploy the organisation didn't test every camera but only 1 in a very large batch, but the stickers were put on all of them. The main reason they did it was to confirm it wasn't a "knock off" of a German product and didn't infringe copyright law.
Regardless of the true nature of the JCII sticker, the presence/absence is, for some buyers, yet another characteristic of a unit 'as it came from the factory', for whatever that might or might not alter the 'value' of that unit...although a beat up camera with JCII sticker would have zero intrinsic increase in value for me vs. one missing that sticker!
The web says of the JCII sticker, "These stickers were attached to camera products that satisfied minimal quality requirements and were not blatant copies of German camera products of the time. The sticker does not mean that the individual item was tested, only that its model had been deemed to be usable and not a knockoff. At that time, goods manufactured in Japan were regarded abroad, often with good reason, as cheap trash or (externally at least) exact copies of patented items made in other countries, and this sticker was an effort by Japanese companies and government to improve their image."