World War I was referred to at the time -- and even still today -- as The Great War, involving numerous countries in Europe from 1914 to 1918. The U.S. was reluctant to enter the war, but due to hostile German actions towards neutral naval vessels, the U.S. finally entered the war in 1917. The cartridges and artillery used during WWI are now considered obsolete, and many of the cartridges found date between the mid 1890s and 1918. Learning to Identify certain attributes of these cartridges is a key in understanding what country they belonged to, and how old they may be.
Identify the cartridge body. The copper cylinders which holds the projectiles produced during this era all have the similarity of not having an extraction groove. A WWI casing will have a case rim, which is essentially the wider base of the cartridge, but no indention above it, which is an extraction groove.
Look at the bottom of the cartridge casing. You should see a few markings depending on the age and surface condition of the cartridge. Look for the date near the centre. If the date is between 1900 and 1918, then you have a round possibly used -- or manufactured -- during the time of the Great War. Some stockpile ammunition from the mid 1800s was used as well, but this can prove difficult to find.
Look at any markings on the casing that indicate a U.S. origin. The U.S. cartridges will have stamped letters in English, and the bottom will typically read "Model of 1916" or "Model of 1914" depending on the year the round was produced. The cartridge will also have its manufacturing company name stamped on the bottom. Cartridges for this war came from numerous ammunition production locations scattered across the country, as the full swing of the industrial revolution was just beginning to take hold, and adequate production plants weren't in place as they are today.
British cartridges typically will have a particular head-stamp marking indicative of the year and manufacturing armorer. The UK had numerous armories in many locations across the globe, so obtaining a head-stamp I.D. catalogue for collecting these cartridges is essential. A cartridge with a head-stamp marking of AF is indicative of a round produced in Melbourne Australia. A marking of BE is indicative of its being produced at the Royal Ordinance Factory in Worcester, both during WWI.
Download guides or images of WWI cartridges to help in your collecting and identification efforts.
Never assume that ordinance is inactive or inert no matter how old it is. Live ammunition can still be found, and can still be deadly many years after it is produced.