The early Tigers had a binocular sight and so there were in the left side of the mantlet.
Later, the design was changed to use a monocular sight, positioned at the same place as the right-hand telescope of the original. The hole for the left telescope was eliminated from the mantlet design.
However, some mantlets waiting in the factories had already been drilled with both holes, and it was likely decided to upgrade Tigers under repair with the new arrangement. Holes had to be filled.
A plug was therefore designed to fill the left-hand telescope opening in existing mantlets. The design dimensions of this unit are preserved (ref 1). Here they are:
This is what the piece looked like:
The stepped shape was designed to match the hole in the mantlet which was also stepped. At most points there was some clearance, but the widest part of the plug was specified at 50mm diameter, exactly the same size as the outermost part of the hole. It is likely that these plugs had to be hammered into place.
Once in place, the plugs were welded at both ends. The vehicle in Saumur has such a plug.