I would like to find out which observations have the same content for one variable. Is there a command for this?

I would like to merge 2 data sets but I receive the message "variable FILE does not uniquely identify observations in the master data". In my master data set I have company observations.
The data set that I want to use for merging contains results of a text analysis. And this Stata file has a variable called FILE. I used files that are named Companyname_AR_year. In the variable FILE this is the same. So in order to do the merging, I generated a variable in the master data set generate FILE=Companyname+"_AR_"+string(year,"%02.0f").
They should be unique, however apparently there is a mistake.
Is it possible to find out which observations have the same name?

Thank you and best regards, Robert