The requested vessel with name SLK999 and MMSI:621420036 and IMO:0 is temporary not in our database.
Perhaps you mean one of the following ships:

Vessel name IMO MMSI In range Destination Last report
SLK168 N/A 621420033 Jan 18, 2018 01:34 UTC
SLK888 8317124 621420034 HK Sep 06, 2017 04:56 UTC

Also, you may try to find the vessel in our comprehensive Vessels Database or track this ship on the map.