There are many different versions of Martinis, but if it is a legitimate Martini-Enfield (i.e. properly converted to .303 in A British arsenal), then the 1903 date, and other relevant markings, should be on the left side of the receiver. When originally made as a Martini-Henry, in .577/.450 (essentially a lengthened .577 Snider-Enfield case, necked down to .450 cal.) the receiver markings would have been applied on the right side of the receiver. Then, if later converted to .303, the markings signifying that conversion were stamped on the left side. If it is a British conversion , the original Maretini-Henry markings should still be present on the right side.
Another possibility - there are also quite a few "Citadel" Martini-Enfields on the market. These were surplus/obsolete rifles supplied by Britain to Egypt in the early years of the 20th century, and should be marked on the left side of the receiver with a "star & crescent" mark, over "Citadel", over the date. In this case, the original British markings on the right side of the receiver would be "scrubbed" - i.e. removed. (The explanation is that, although Egypt was very much within the British "sphere of influence" - so Britain could control the Suez Canal - it was still officially part of the Turkish Ottoman Empire, so it "wouldn't do" for British-marked firearms to be supplied to them. The "Citadel" mark denotes the arsenal at "The Citadel", the main Egyptian military installation at that time, located in Cairo.)
A third possibility, especially if the 1903 date appears on the right side of the receiver, is that it could be a "Khyber Pass Special" - meaning a hand-built copy produced under primitive conditions in that area of the world. The "craftsmen" who made them often did an incredibly good job making them look right, but they weren't up on what dates should appear on that side of the receiver (e.g. 1903 would be wrong there) - also, it is questionable whether such a copy would be safe to fire.
Can you post any clear pictures of the markings?