The Tiger 1 had a gun mantlet in the form of a horizontal cylinder attached to a flat plate. The cylinder, of 390mm radius, was mounted within the turret front armour.
This sectional diagram shows the mantlet and turret front armour of an "early" turret. The forward direction of the vehicle is to the left. The frontal armour plate is 100mm thick and slanted at 5 degrees. Green dimensions are quoted directly from surviving design plans; blue ones are scaled from diagrams and may be one or two millimeters wrong. The diagram shows a slice of the mantlet at the opening for the coaxial MG. The mantlet contains an internal plate, at lower right, to which the MG would be bolted. There is a metal frame attached to the inside face of the armour, meeting the edge of the mantlet 75mm back from the axis, where the mantlet's waterproof seal can be attached.
Looking at the lower part of the above diagram, you will see that the lower part of the turret front armour is carefully shaped to follow the curve of the mantlet. This prevented 'splash' from entering the turret when the vehicle was hit. However, it would be impossible to shape the upper frontal armour in the same way, because then the hole for the mantlet would be wider in the middle than at the front or back, and the mantlet could not be inserted or removed.
This diagram has the turret front armour tilted vertically so that you can see it more clearly. On the left, you will see how the problem was solved in the first design of the turret. A removable metal bar is bolted to the top outer face of the armour. When this bar is unbolted a clearance of 200mm is revealed, just enough that the mantlet can be lifted out the front of the turret.
This partially complete model illustrates what the metal bars looked like in an "early" turret. There were in fact 3 bars, of 470mm length. They were held in place by countersunk hex-head bolts.
The Tiger's turret was redesigned and significantly simplified at one point. One of the changes was to stop making turret frontal armour with a curved profile. On the right hand side of the diagram above, you will see how the "mid" and "late" turrets were shaped; the sides of the opening are flat, providing no splash protection. Instead there are two identical sets of metal bars, above and below. In the diagram, I have removed the lower bars to show the notch where they sat.
This drawing, with dimensions quoted from German originals, shows the splash guards seen face-on.
These photos of the surviving vehicle at Vimoutiers show the splash guards above and below the mantlet. You can see that the upper one is quite prominent and should be represented on 35th scale models. Unfortunately, even the newest Tamiya kits have a mantlet whose diameter is too large, making rework difficult.
[2] Factory drawing: Turmgehause 2AKF31861U1B11 (overall turret armour)
[3] Factory drawing: Turmgehause 2AKF31861U1B12 (turret front plates)
[4] Survey of vehicle at Vimoutiers, by Jean-Charles Breucque
[5] Survey of vehicle 251114, at Saumur, by Jean-Charles Breucque