Interpretation of second character Here's a picture I have found on flickr, taken in an outdoor museum in South Korea. 
I can only recognize the 1st, 3rd and 4th characters: 寶X山房. 寶 is probably not the variant written on the wooden board, but it's the same character. What is the 2nd character?

The original high resolution image is here. 

 

EDIT： My best guess is 丁, but why this odd curvy shape when the rest of the characters are rendered fairly standard?
It looks like it is indeed 丁. The Flickr link mentioned the photo was taken at 茶山草堂. With that information, I was able to find another site with a photo of the same doorway indicating that it says 寶丁山房.

I don't know the specific reason why the character is stylized in this way, though 茶山 refers to the pen name of Joeng Yak-yong (丁若鏞), so it could be in reference to his surname, 丁.