5.82C in the Radio Frequency Table Allocation of Ireland.

Content Type
ITU FOOTNOTE
Title
5.82C
Description
The frequency band 495 -505 kHz is used  for the international NAVDAT system as described in the most recent version of Recommendation ITU-R M.2010. NAVDAT transmitting stations are limited to coast stations.     (WRC-19)
Source
https://search.itu.int/history/HistoryDigitalCollectionDocLibrary/1.43.48.en.101.pdf