Mistaken Identity - Shiva Crescent Moon
Among the assortments of weapons worn by members of the Nihang sect in their turbans is an emblem called the Aad Chand that is often mistaken by some as a stylized or old style khanda emblem. This symbol in not a khanda emblem but one that is unique and specific to the belief system of the Nihangs.
Shiva and the Nihangs
Seen in early 19th century images of Nihangs, the design of the Aad Chand emblem has remained relatively unchanged over time. The Sanskrit word ‘Ardh’, meaning half is written as ‘Addh’ in Punjabi. The Sanskrit word ‘Chandra, meaning moon is ‘Chand’ in Punjabi. Aad Chand literally means ‘Half Moon’. 
There are two major variations of the Aad Chand worn by Nihangs. The more common one features a crescent moon symbol with a khanda sword at its center and decorative elements below the crescent. The other less common variation featuring three bladed weapons (two curved swords on either side of a central khanda sword) all within the crescent moon. This second variation is called a Gajgah and is traditionally worn by Nihang warriors who have proven themselves on the battle ground. 
In Hinduism the crescent moon referred to as Chandra is an ancient lunar deity often associated with the the Vedic Lunar deity Soma. Soma is connected with dew, and as such, is one of the gods of fertility. The crescent moon symbol is always depicted worn on the head in images of the Hindu God Shiva.
Shiva is considered one of the primary deities within various Hindu traditions. Within the Trimurti school of religious thought, Shiva is regarded as the destroyer or transformer. The iconographic association of the moon symbol Chandra on Shivas head date back to the time of the rise of Shiva and his close association with the older Vedic god Rudra. An association between Rudra and Soma can be found in a hymn in the Rig Veda where Soma and Rudra are jointly implored, and in later literature Soma and Rudra came to be identified with one another, as were Soma and the Moon. 
Within the Nihang tradition, the wearing of the crescent moon of Shiva is regarded by some members of the sect as an integral part of considering themselves as Shiv Saroop, the very form of Shiva. 
Although the crescent moon appears to be a standard element of Shiva iconography, the khanda sword at its middle is not found in images of Shiva. Wearing of the khanda sword within the crescent moon of Shiva has been a popular design variation among the Nihangs. Origins of this implementation remain unclear as the Nihang sect has mainly had an oral tradition. Very rare thousand year old Chola dynasty Shiva tridents from South India in the shape of crescent moons with a khanda sword like center element have a similar appearance, but to date, no direct documented association between the two has been found.
The relationship between the various elements of the Aad Chand symbol as understood and explained by the Budha Dal, the oldest faction within the Nihang sect is as follows:
There are a wide range of complementary understandings all which allow one to analyze the interaction of Shiv-Shakti within the Nihang Singh at various levels. Shiv is believed to be represented by a half moon (Aad Chand), signifying calm and coolness. Shakti is represented by a sun and is believed to be a more powerful energy and the driving force of the universe, within the Sikh tradition Chandi (personification of shakti) or Durga is not worshipped as a deity, but in the form of Bhaguati (sword). The Aad Chand (crescent moon) representing Shiv has long been a trademark of Nihang Singhs as is the wearing of arms; representing the divine union of Shiv and Shakti. 
With the emphasis on the sword (Bhagauti) as a reference to God, as the ‘Divine Sword’ in the poetry of Guru Gobind Singh, the Nihangs may have used this symbolic interpretation in their incorporation of the khanda sword within the Shiva crescent moon of their Aad Chand emblem.
Another less common interpretation based on interviews with Budha Dal members conducted in 1992-1993 indicates a interpretation of the Aad Chand emblem as a fertility symbol.
The Add-Chand is made up of two components; the Chand is the Cresecnet moon, and symbol of female fertility, whilst the central piece is a shivling (phallus) and potent representation of Shiva. Note that below the shivling are two balls rather than the hilt of a khanda as there are in the Sikh symbol. 
A similar interpretation also appeared in the description of an antique Aad Chand emblem sold by a major auction house.
The Add-Chand symbol was adopted by the Nihang Sikhs in the 17th century and is worn on the 'Dumaala' a type of turban specific to the Nihang. It is made up of two components, the Chand or crescent moon which symbolizes female fertility and the Shivling, a phallic symbol and potent representation of Shiva. 
The Shivling phallic symbol as depicted in Hindu religious iconography is typically a smooth rounded cylinder, while the vertical element used by the Nihangs in their Aad Chand emblem has pointed edges and a flat appearance similar to the blade of a sword.
A third interpretation of the Aad Chand emblem is presented by a member of the 3HO, Sikh Dharma International sect. Some members of this sect are also known to wear the Aad Chand emblem.
The Chand is a moon, representing deva Chandi yoni. Shiva is all the time shown wearing a moon or even Chandi deva on his head. Because Shiva is Master of Yoga, and union of Shiva and Shakti are the awakening of kundalini consciousness it relates specifically to yogic principles…So the Shiva is always shown with this same moon. Nihangs traditionally wore on the forehead at area of third eye, 6th agni chakr. That is where the kundalini must be moved into the house of the moon before it rises into the wrong channel. So a dumalla with this adhh Chand symbol shows a yogi who has mastered his senses and does not act from krodh or selfishness. It shows that he has raised his kundalini shakti and has powers for the battlefield like a feared siddhu. It shows that he has properly moved his spiritual energies into the house of Chandi. 
1. Amrit Pal Singh 'Amrit', http://www.amritworld.com/main/?p=964
2. Nihang Teja Singh, http://www.flickr.com/people/chitrakari/
3. Wikipedia, http://en.wikipedia.org/wiki/Shiva
4. Nihang Teja Singh, http://www.flickr.com/people/chitrakari/
5. Baba Fateh Singh, Jatha Nihang Singha, an international wing of the Shriromani Panth Akali Budha Dal, http://www.nihangsingh.org/Shiv-Shakti.html
6. Amandeep Singh Madra, Tapoban.org forum, Topic: CHAND-TORA?, Oct. 1, 2004 - Dec 13, 2004
7. Christies auction, Lot 62, Sale 5094, Lot Notes, Islamic Works of Art, 20 April 2007
8. Harjas Kaur Khalsa, http://www.sikhism.us/sikh-sikhi-sikhism/22256-signifance-of-chand-toda.html