Olympic Stamps Album And Autograph! (Sohn Kee-Chung - 1988)

Here's a difficult one.

I have this album of from the Olympic games in Korea 1988, which I can probably get $50 for, considering what I have seen on the market. However, additionally my grandfather got Sohn Kee-chung's autograph in it (Debatable the biggest Korea sportstar ever). I have found examples of Sohn Kee-chung's autograph going for around $120.

So how can I possibly valuate this kind of album, and please feel free to give an estimate of what you might think it's worth.

This is rather difficult for collectors who may not collect Korea. I would not be able to give any type of value but I suspect that there may be a Korean Stamp Society of sorts especially in Korea. My lowly advice is to try to find other Korea collectors and start a conversation there. Something like this: https://koreastampsociety.org/
Good luck