I need help on an issue that I can not fix myself.

I have created a halve of a chess piece - Knight in poly. I then duplicated it and then combined the two pieces in to ine poly object.

The problem is that when you do so it makes a nice piece of geometry but in shading mode you will see a specific line on where the pieces were combined.

[See attachment] - the yellow dotted vertex is the line where it shows the two different geometry.

I have searched this forum on how to fix this but as far as I can see it that I have to manually merge each vertex :-S

How can I fix this issue ?