ah , yes it has that little ship look , the army had a couple of alloy acts , one turned up in strangford lough for a few weeks and then vanished ,,,Most of the Cats I fit out/work on are GRP but that one was all Aluminium. I believe it was built in Australia, whether it came over here new or was bought second hand I am not sure. It is used as a survey boat and is owned by Forth Ports.
Have you seen Polar Bound , buily by David Scott Cowper ,,, for a man who welds alloy boats , its really well worth a google and a read , there were a couple of articles on it when it was built . I looked at buying Mabel E Holland at one point , but after reading North west passage solo , decided against the idea.