Thus making it second hand information. The overall majority of information in the world is second hand documentation/information, If you take a piece of paper and write " The grass is green" and then hand it to someone that hasn't seen you actually write the note yourself then it's second hand information.

Now second hand information might be unreliable because of it, however if you then also recieve other second hand informations about the same subject and very little to contradict it then the reliability that the info is correct increases. Which it needs to be since first hand information is only presented to those that actually witness the information firsthand, while if they then tell others who were not present about it then it becomes second hand information.

So if you did post a picture of your knob and others verified it then it would be second hand information since first hand information would be to have it shown while we were in the same room as you. Likewise with North Korea. We can't say with a 100% accuracy that North Korea is the way it is from the pictures and witness statements told us, However with the large amount of info that shows the same result and little that shows otherwise then we'd need to consider the images and statements as credible, most cause none of us have actually been in North Korea and seen their "knobs" for ourselves.

There exists pictures that show that is the case, witness statements from people who's left North Korea.

Granted none of us has actually been there and seen it for ourselves, mainly cause the country has shut itself in. So wether it actually is like that or not is unknown for both me and you and so we'd rely on smuggled out pictures and statements to paint a picture of how it might be in North Korea.