Dean, Ok *PHEW* at least its not just me. I'll never knock someone who knows more then me, thats not too difficult, but this is so far beyond me thats why I said what I did in my previous post.
David, thank you. Now that makes sense. Yes, his are closer to the Tiger 1's and yes, it should be a smoother block as shown. This makes these very easy to scratch build something close if you don't care about what can't be seen inside. Not that hard to do Jack and it really adds to the tank I think. I use Tamiya clear green and plastic packaging to make mine. They are not hollow just paint the green on the inside of the plastic and glue to styrene and you get the perception of depth from it. If you really want it to shine paint the styrene silver before putting down the green plastic...
"There are things in Russia which are not as they seem..."
Georgy Konstantinovich Zhukov
Thanks everyone for your replies - far more info than I would have believed possible on periscopes but now my mind is made up - I will have a crack at scratch building some so that they look convincing once installed and enhance rather than detract from the overall look.
Tamiya King Tiger (no options)
Taigen Full Metal T34 (winter)
Heng Long Challenger II (European camo')
Tamiya Tiger I full options (still in the box)