Need observations across two datasets identified

I have a dataset that I built from a master dataset. I merged about ten other datasets into the master dataset in Stata but somehow I have 26 extra observations from when I merged the datasets. So the original dataset has 9852 observations but the dataset I built has 9887 observations. I need those extra 25 observations identified and then deleted. The dataset has semi-unique dispute numbers and the countries involved and entries for each year, which should make it easy to identify and delete the extra observations. It should be fairly easy to identify which observations are in the dataset I built compared to the original dataset. I just don't know how to do it.