Navy MARK/MOD Nomenclature System
The Navy assignes MARK/MOD numbers to nearly all types of equipment not covered by other designation systems, e.g. torpedoes, mines, guns, missile launchers, etc. This MARK/MOD system has its origins in the early 20th century, and was formally adopted in 1944. Of course, it was revised and extended over time, and the current standard is defined in MIL-STD-1661.
Similar in concept to the Army Nomenclature System, the full nomenclature for an equipment item consists of a type name and the MARK/MOD numbers. Examples are:
Examples:
Torpedo, MARK 46 MOD 4
Fire Control System, Missile, MARK 99 MOD 0
Mount, Gun, 8 Inch, MARK 225 MOD 1
Launcher, Missile, EX 31 MOD 0
(1) (2) (3)
(1) is the name of the item, which is part of the complete nomenclature. According to MIL-STD-1661, the name is to precede the MARK number, and separated from the latter by a comma. The name should be selected from DoD Cataloging Handbook H6 ("Federal Item Name Directory"). In tabulated equipment listings, the item names should be written in "inverted nomenclature", in which the usual order of words in the name is reversed (as in the list of examples). That way, related items will be grouped together in alphabetical listings.
Number (2) is the MARK number. MARK numbers are assigned in numerical sequence within each equipment category. The prefix EX instead of MARK is used for experimental or developmental items. If an EX item is adopted for operational use, it will use MARK afterwards, but will keep the assigned number.
Number (3) is the MOD number, which indicates a modification or variant of the equipment. MOD numbers are assigned in numerical sequence for each equipment, the initial version being designated MOD 0. When an item is redesignated from EX to MARK, the MOD numbers for "MARK" are restarted from Zero.
An example will clarify this: An experimental item is designated EX 44, and the MOD numbers 0 through 5 were assigned during development. Now it is decided to put MOD 1 and MOD 5 into operational service. Then EX 44 MOD 1 would be redesignated MARK 44 MOD 0, and EX 44 MOD 5 would become MARK 44 MOD 1. However, if all (or nearly all) MODs of the EX series are to become operational, the MOD numbers can be retained for the MARK series, the (few) unused numbers being left unassinged in the MARK series.
The general guideline is to write the words MARK and MOD unabbreviated and in uppercase. However, abbreviation of MARK as MK and/or use of mixed-case (Mark/Mod) lettering is explicitly allowed. Dashes and other punctuations should not be used. Therefore, all the following variants are correct nomenclature:
Torpedo, MARK 46 MOD 4
Torpedo, MK 46 MOD 4
Torpedo, Mark 46 Mod 4
Torpedo, Mk 46 Mod 4
The following variants do not conform to the strict rules of MIL-STD-1661, but are nevertheless quite common:
Torpedo, Mark-46 Mod 4
Torpedo, MK-46 Mod 4
Torpedo, Mk.46 Mod 4
