A very common Korean document with revenue stamps attached is this type of document: a 약속어음 or promissory note. It registers both a giver and a receiver of money and shows who will have to repay to whom, including the amount of money involved. Notice how the name of the type of document is written on the document itself in a combination of Chinese characters (or hanja in Korean) and Korean characters (hangul/hangeul): 約束어음.
The document has one revenue stamp for 100 won on it. That’s the standard rate for the type of document it was used on, but it is relatively expensive in this case as the amount due is only 250 won.
The stamp is listed as RP67 in the “Korean Postage Stamp Catalogue” (KPSC). The publication date is according to the KPSC 17 April 1972, but that is impossible given that the document shown here was signed on 17 September 1970.
(Names have for privacy reasons been digitally deleted.)