IMO numbers: vessel built 1973 with IMO 4500163

[dirk septer]

How are IMO numbers generated?

How can a vessel built in 1973 have an IMO of 4500163?

https://www.shipspotting.com/photos/3458929

[davidships]

Suspect that COCKCHAFER, as a naval auxiliary, was not in Lloyd's Register when LR/IMO unique numbers began, so would have received a number later - perhaps in 2001, though possibly earlier.  Some of these were given numbers in the 4xxxxxx series; others, mainly yachts, in 1xxxxxx series.  Since 1991 allocated numbers have been entirely without "meaning" - they are just a number.

[ALAN]

I also get confused in how registration numbers are allocated to military warships.  As you say the COCKCHAFER has been allocated 4500163 which is in fact not an IMO number as was SCARAB 4909393 but the others BEE, CRICKET, LADYBIRD and CICALA seems to be issued with IMO numbers but I have not been able to find what GNAT was allocated.  I can find no reference or site where warships are allocated their non IMO numbers which begin with 4****** and therefore do not know where photographers who post there pictures on this site get these numbers from.  These non IMO registration numbers are not displayed on the ship as IMO numbers are displayed on merchant ships in fact warships along with certain other vessels are not allocated IMO (See https://en.wikipedia.org/wiki/IMO_number). Maybe there is someone out there who knows where warships Non-IMO registrations numbers are issued and where they can be found.

BEE                   8891015
CRICKET           8878051
COCKCHAFER   4500163
GNAT           ??
LADYBIRD           8891027
CICALA           8891443
SCARAB           4909393

[Robert J Smith]

"Miramar Ship Index" use IMO numbers in its index but generates their own ID number for those without IMO numbers most of which begin with 4. Shipspotting quite regularly accepts these numbers as IMO which keeps all the photos together.

The "Miramar Ship Index" requires a small fee but is well worth it when looking up older vessels.

[davidships]

GNAT, later NORTH STAR then ULISSES I, is IMO 8878063 - consecutive to CRICKET

[ALAN]

Thanks Davidships have updated my spreadsheet with your valuable information.

Regards

Alan

[Kyle Stubbs]

The numbers issued by IMO to naval vessels can all be found in the IMO's public access GISIS Ship and Company Particulars system, even if the vessel descriptors are a bit hit-or-miss.

For example, a query for the US Navy destroyer "Zumwalt" finds the following vessel:

ZUMWALT
IMO #: 4676766
Type: Yacht
Type (detailed): Destroyer