Nice find, these are supposedly an Ottoman military helmet from the mid 1800's, from what I have read the ruler of Egypt at the time was an Ottoman officer (Muhammad Ali) who had proclaimed himself to be the "khedive" of Egypt, this is a very interesting bit of middle east history, anyone with an interest in the Ottoman Empire should do some reading on it. There is a web site by an author who has researched ottoman uniforms from that era, he has written a book on the subject, I have posted a link. These helmets are pictured as being worn with a cuirass also.
Can you post images of the liner and interior of your helmet as these helmets are rarely seen.
This style of helmet is said to have been used by the body guards of the Khedive of Egypt.
http://en.wikipedia.org/wiki/Khedivate_of_Egypt
http://en.wikipedia.org/wiki/Muhammad_Ali_Pasha
Ottoman uniforms
http://www.ottoman-uniforms.com/crim...kish-uniforms/