According to Wikipedia, the very first photographic portrait of a human was a self-portrait taken in October or November of 1839 (see their "History of Photography" page). The subject and photographer was Robert Cornelius.
Since Lincoln was born in 1809, he would have been 30 in 1839. Consequently, it is just barely possible that your photo could be of Abraham Lincoln although he would have to have been at least 30 when your photo was taken. An age of 30 is not all that different than your Lincoln experts' estimate of 27 to 29 so it is possible that your photo is of Lincoln.
Photography was really just getting started in 1839 and the technology was changing quite rapidly. Consequently, an expert in early photographic technology might be able to provide a reasonably accurate date range for when your photo was probably taken.
Since Lincoln was born in 1809, he would have been 30 in 1839. Consequently, it is just barely possible that your photo could be of Abraham Lincoln although he would have to have been at least 30 when your photo was taken. An age of 30 is not all that different than your Lincoln experts' estimate of 27 to 29 so it is possible that your photo is of Lincoln.
Photography was really just getting started in 1839 and the technology was changing quite rapidly. Consequently, an expert in early photographic technology might be able to provide a reasonably accurate date range for when your photo was probably taken.