A remarkable degree of consistency can be found in the types of helmet typically worn in Punjab during the 19th century Sikh Empire. Corroborating visual evidence, written accounts and surviving helmets from Punjab all point to an overwhelming preference among the Sikhs of 19th century Punjab for the Indo-Persian style helmet.
The famous British author, Charles Dickens while visiting Amritsar as a tourist in 1881 was approached by a street vendor selling an old Sikh helmet. The helmet turned out to have been from the Lahore armoury of Maharaja Ranjit Singh and the description that Dickens provides of the helmet is an excellent example of the characteristics of a typical Sikh helmet:
My servant spoke with him, and presently asked: "You want buy Indian man's head thing sah'b?" Before I could demand an explanation, the child undid his bundle, and displayed a beautiful helmet, of the old Sikh form, familiar to most people. It might be described as a bowl-shaped cap of polished steel, fitted with three long plume-sockets, one at the crown, and one above each brow. A heart-shaped piece of metal, at the end of a stout shaft, protects the nose; playing through a loop, which is fitted with a catch, it may be drawn up and secured when no danger threatens. All round the cap brim descends a curtain of chain-mail, short over the ears, but long enough behind to guard the shoulders and the back. In this specimen, the nose-piece, the plume-sockets, and an inch-wide circlet round the brim, were finely inlaid with gold, whilst the curtain was adorned with golden links disposed in an effective pattern. (Dickens, 1881) 
Elements of Typical Sikh Helmet
An old Sikh helmet that was collected from the battlefields of Punjab during the Anglo-Sikh Wars and taken back to England by a British soldier as a war souvenir and which is today in a private collection, illustrated the various design elements of a typical helmet from the Sikh Empire:
1. Charles Dickens, "A Traveller's Tales", All the Year Round, January 22, 1881, 320-321