Elias Ingraham formed a number of different business partnerships during his years as a clockmaker. All the ventures incorporated the Ingraham name but there were a number of variations used during different time periods. This fact can help you date an Ingraham clock, usually to within a few years of its manufacture.
First check the back of the movement for a stamped name. If you don't find it on the back, you may have to remove the movement from the case so that you can check the front plate for a stamp.
Below are the different business names and the dates used:
1844 - Brewster & Ingrahams: a partnership between Elias Ingraham, his brother Andrew, and Elisha Curtis Brewster.
1852 - E. & A. Ingrahams Company
1857 - Elias Ingraham and Company
1861 - E. Ingraham & Company
1881 - The E. Ingraham & Company
1885 - The E. Ingraham Company
You can also check the movement for a set of numbers stamped on the front plate. The first one or two digits identifies the month the clock was made. The second two digits tell you the year the clock was made. For instance, if you find "2 75", it would mean the movement was made in February, 1875. If you fin "11 03" it means the clock was made in December of 1903. And so on.