Right - A headgear plate with the 'SM' monogram of Mohamed Sa'id Pasha of Egypt 1854-1863 (from the website Egyptian Royalty). The plate measures 138 x 150 mm, and is correctly shaped for a short-lived bearskin cap, or 'hussars' colpack cap used in the 1859 period, for the Khedive's household guards.
Above - Photographed recently, an Egyptian cuirassier helmet likely from the 1859 Khedive Life Guards. The text on the helmet plate is likely to be "Muhammad Sa'id" (see below).
Right - The helmet plate Arabic script (seen above) is identical to "Muhammad Sa'id", the 'Wali of Egypt and Sudan', from 1854 until 1863, used in various court paintings of him.