The give away could be, if you go to the enlarged picture, and have a look at the mast and compare its diameter with the wooden door on bridge, you will see that the mast diameter looks to be larger than the width of the door. So anyone who is used to scaling off pictures will know that the diameter of the mast will be larger than the width of the door - average door 2 foot 6 inches - 3 foot wide. So therefore the mast must be in the region of 3 foot - 4 foot in diameter. But, if you look further up the mast - where the mast is painted black, you will see foot and hand grab rails for working on the exterior with the main mast support. This indicates there could be either a door on the back end of the mast, or a welded runged ladder all the way up the back of the mast right to the top of the observation platform which I tend to favour.
zet