I cannot see the pictures but I have to tell you that if the location is Ushuaia information is being shown is completely inaccurate when not false.
My father works in the argentine navy and until February 2006 in the base naval Ushuaia, he was the BNUS vice commander, none of Malvinas islands battles took place in Ushuaia. There was almost a war between Argentina and Chile in 1979, perhaps some of the cannons you've seen where left there since that time but it is quite difficult. I will ask my father Im sure I will be able to give you further info about the issue.