From what I can gather from the picture, it looks like a legit 1603. However the pics are too small to finally say youre good to go.
Beware of the pitfalls with the four-digit references and that this is the 1570 movement with non- quick set of the date:
Look at this thread:
https://www.rolexforums.com/showthread.php?t=455049
BR
Torsten