This is the 2485th most frequent Polish word.
ipn
IPN: Institute of National Remembrance, a Polish institution researching and documenting the nation's history, particularly regarding WWII and communist-era crimes.
Here, IPN refers to the 'Instytut Pamięci Narodowej' (Institute of National Remembrance), which is a specific organization in Poland.
IPN współpracuje z historykami, aby dokumentować memorie przeszłości.
The IPN works with historians to document memories of the past.
Here, the use of 'IPN' continues to specify the Institute's archives, clearly indicating it as a proper noun.
Znajdziesz te materiały w archiwach IPN.
You will find these materials in the IPN archives.
In this sentence, 'IPN' again refers to the institution and its role in making decisions relevant to its purpose.