In my previous reply, I put the question mark as I thought different systems might have been used on different engine models - a 9E with dynastart, for example, is a very different animal from a 6E!
My own 6E has the number on the front mount, and I have no reason to think that it's not original.
It's on the very front of the engine mount - facing straight forwards, as it were - stamped in there when the engine was "loose", before it went into any mounting frame.