"Like most good things, Cairns got its start with very humble beginnings. The founder, H.T. Gratacap, had carved a niche in an innovative ocean transit luggage market, making his luggage from specially treated leather so it would offer superior durability and withstand wetness without rotting. Being a volunteer Firefighter in New York City, he and his compatriots became aware of the need to provide Firefighters with better head protection. Gratacap rose to the need by inventing the first American fire helmet in 1836. That helmet was named the New Yorker, and although being re-engineered many times through out it's life, it is still produced today.
Shortly after this, two brothers named Cairns, who were operating a Metal Badge, Button, and Insignia business in New York, came up with the idea to mount an identification badge to the front of Gratacap's helmets. Hence the first front piece and holder. The match was made, and the companies cooperated until Gratacap retired in the mid 1850s, and the Cairns & Brother legacy began. At this time, the business was known for the manufacture of a rigid head protection device made out of leather and very ornate helmet identification shields known today as front pieces. Not inclined to rest on their laurels, the Cairns brothers and their nephews began to expand the product lines to encompass nearly all of the Firefighters' contemporary equipment needs. Through the late 1800's, the company extended its line to meet all fire department equipment needs except for trucks and ladders. By the turn of the century, this line included a full line of head protection devices, uniforms, badges, belts, buckles, fire record books, protective clothing, some respiratory devices and other equipment like tools, axes, hose, lamps and torches."
So I would guess it's from about 1900 or later. It certainly looks like it's been in the ground a while, but the design and style is exactly the same as used today. If you polished it, it could go on my service jacket and nobody would know the difference.