The kit contains two transparent periscopes, part L4, for the driver and radio operator. The periscopes install in the crew hatches in the hull top.
You may wish to correct a small problem with the shape of the parts. The top end of each periscope is molded square, but in fact it was a copy of the bottom end and should have a slanted back face.
The above diagram (after a British intelligence report) shows the top of a periscope under its metal cover in the hatch.
Dragon have molded these periscopes in clear plastic. The real periscope was made of glass but of course it had a protective casing; this was a dark brown plastic-like substance, possibly Bakelite.
The best approach to painting the part is to paint an inside colour on the opposite sides to each window; then mask off the windows and paint the whole thing Dark Brown. The inside colour is not known to me, but Silver would probably not give a realistic effect. Look at this example of a similar periscope.
