66 ft land measuring chain of iron with brass handles consisting of 100 links. The handles are stamped “4P” (4 lb tension).
This type of chain is also known as a Gunter’s chain (or measurement) is a distance measuring device used for surveying. It was designed and introduced in 1620 by English clergyman and mathematician Edmund Gunter (1581–1626). It enabled plots of land to be accurately surveyed and plotted. For more information see https://en.wikipedia.org/wiki/Gunter’s_chain.
The chain is 66 feet long and is divided into 100 links, each 7.92 inches long. The length of a chain is the total length from outside to outside of the handles. At every tenth link is attached a distinctive tag or tally of brass of the patterns shown in the figure. As each tag represents its distance from both ends of the chain, either handle can be regarded as the zero, so that a little care is necessary to avoid misreading. In taking readings between tags, one must count the number of links from the previous tag, estimating fractions of a unit if necessary. The use of the chain for surveying was largely discontinued during the first half of the 20th century. However although the chain was ideal for measuring over rough arable and grassland, there was a problem that, after considerable use the links in the chain became extended making it necessary to check and correct its length against a standard regularly.