Archaeologists use the exponential, radioactive decay of carbon 14 to estimate the death dates of organic material.
The stable form of carbon is carbon 12 and the radioactive isotope carbon 14 decays over time into nitrogen 14 and other particles.
1) all the shells with fixed bails to hold the chinstrap have been produced during WW2, from April 1941 to October 1943, then started the production of swivel bails.
In both cases the straps are stitched to the loops.
In that system, it is 2009 - but should one say ad 2009 or, as is increasingly common among scholars, 2009 CE - 2009 of the 'Common Era'?
The Common Era retains a Christian reference point - the birth of Christ - but this may be regarded as a historical accident of globalisation.
Under the brim there is a number indicating the production lot.
According to the Muslim lunar calendar, dating from Muhammad's Hijra (flight or emigration) from Mecca, it is now ah 1430.As former UN General Secretary Kofi Annan put it in a statement marking the turn of the millennium: The Christian calendar no longer belongs exclusively to Christians.' For some, these are fighting words: the Southern Baptist Convention resolved, also in 2000, to resist the 'revisionism' implicit in the CE/BCEsystem and to retain AD 'as a reminder to those in this secular age ... The AD/BC chronology is not so ancient as some proponents suppose; nor is the CE/BCE system so recent.For the first five centuries of their religion, Christians marked time according to local conventions, usually from the legendary foundation of Rome (753 BC), or from the Diocletian reforms (284 AD).When an organism dies it ceases to replenish carbon in its tissues and the decay of carbon 14 to nitrogen 14 changes the ratio of carbon 12 to carbon 14.Experts can compare the ratio of carbon 12 to carbon 14 in dead material to the ratio when the organism was alive to estimate the date of its death.This is true for Mc Cord Radiator manufactured shells, however all Schlueter shells have been produced during WW2.4) and last, also the color, the texturization and the shape of the shell indicate its age.