A question that is raised time and again is whether Clint Eastwood's character is intended to be the same person in each film of the Dollars Trilogy. Although he is known as the 'Man With No Name' he does in fact go by a different name in each of the films - 'Joe' in 'A Fistful of Dollars', 'Manco' in 'For a Few Dollars More' and 'Blondie' in 'The Good, the Bad and the Ugly'. But two of these names are clearly nicknames, and perhaps so is the third. This therefore proves little.
I believe that Leone was more concerned with the iconic imagery of the 'Man With No Name' than any development of him as the same character throughout the trilogy.
But a further question is commonly raised. What is the correct order of the films in terms of the chronology of the events they portray? Let's look at the evidence.
1. Firstly - and the thing that most people pick-up on - in 'The Good, the Bad and the Ugly', the 'Man With No Name' is seen to acquire his famous poncho towards the end of the film, suggesting that events here pre-date the other two movies, where he wears the poncho throughout.
2. 'The Good, the Bad and the Ugly' is set during the American Civil War that ran from 1861 to 1865, and Arch Stanton's grave is marked 1862. Furthermore, if you look very carefully, you can spot a gravestone in Sad Hill cemetary marked 1864, thereby narrowing the period down to the final two years of the conflict.
3. In both 'A Fistful of Dollars' and 'For a Few Dollars More' the 'Man With No Name' uses a Colt Single Action Army revolver, commonly called the 'Peacemaker'. This was first introduced in 1872.
4. In 'A Fistful of Dollars' we can clearly see a gravestone marked 1873.
5. The newspaper archive that Colonel Mortimer refers to in 'For a Few Dollars More', to investigate Manco's identity, is dated 1873.
Therefore events in 'The Good, the Bad, and the Ugly' must take place at least eight years before the other two films.
So how about the chronology of 'A Fistful of Dollars' and 'A Few Dollars More.' The simple answer is that I don't have a clue, other than they are both set in some period from 1873 onwards.
At the end of the day, don't worry about it ... the films stand alone ... enjoy them for what they are.