Eamon de Valera is shown surrendering with the General Post
Office garrison after the Easter Rising. However, he was actually Commandant of the garrison at Bolland's Mills, which surrendered after the GPO upon receiving orders to stand down. He was never at the GPO during the Rising.
In the Croke Park scene an armoured car opens fire on the crowd. In reality an armoured car was never used at Croke Park.
Thomas MacDonagh surrendered at Jacob's Factory; he wasn't present with GPO leaders Pearse, Clarke or Connolly when they surrendered at 16 Moore Street.
During the Easter Rising scenes, Michael Collins is shown wearing the uniform of a full Lieutenant in the Irish Volunteers. While there is a photo of him in his Volunteers uniform as a Lieutenant, by the Easter Rising he had been promoted to Captain, where he served as aide de camp to Joseph Plunkett, who is conspicuously absent.
Michael Collins is shown wearing a wrist watch. These were developed specifically for World War I airplane fighter pilots. It is far more likely that Collins would have carried a pocket watch during the period the film covers.
The car that de Valera gets into after arriving by boat has the registration 15 D 1, which indicates that although it is a 1915 car, it was imported and registered in Dublin as a historic vehicle sometime after 1987. An original Dublin registration of the time would be in the format IK 1234.
During the raid on Four Courts, over the shoulder of the leftmost soldier a 1980s-vintage bus can be seen.
During the "Croke Park" scene in Bray, the DART lines are visible in the background.
One of the sailing vessels pictured in the background as Collins, Boland, and Kitty Kiernan walk along the pier in the Dun Laoghaire Harbour is a Dublin Bay Sailing Club Mermaid. This class of three-man racing dinghy was designed in 1932, nine years after Collins' death.
When Michael Collins returns from London after the negotiation, he rides a car with Harry Boland and the head of a woman can be seen through the back window. The woman walks at the same speed as the car and remains seen in the same corner of the window, even though the car is increasingly speeding throughout the shot.
After they break out Eamon de Valera from prison and are driving away in the car, there is a brief shadow directly behind de Valera clearly showing the outline of a microphone in a shock mount.
During the Easter Rising scenes, the Volunteers and Citizen Army are shown marching out of the General Post Office to surrender. However, the day before the surrender, they had retreated from the burning GPO to another building down the road, and surrendered from there. The white flag of surrender was actually displayed at 16 Moore Street, in another part of Dublin, where the leadership was residing.
When the cabinet are trying to convince Collins to engage in civil war Arthur Griffith says 'They have occupied the GPO, O'Connell Street, Limerick....'. O'Connell Street was only so named in 1924. In 1922 when this takes place it was still called Sackville Street.
Ned Broy provides to his new boss a picture of Michael Collins, but that same picture was taken from the same archive which Collins previously removed from his own file, a few scenes earlier.