Mysterious hallmarks on unusual case

[Ben.unwin]

Can anyone help me identify what this is and the marks mean? I have no idea where this is from or even if its silver! Any help appreciated.

[Theoderich]

it is Porto

[Ben.unwin]

Thanks! I've searched for hours with no results. Do you know what the other marks mean?
Many thanks Ben

[AG2012]

Hi,
Shield with crowned letter P and two laurel branches silver hallmark for Porto mark used 1843 - 1853.
Tremolierstich ( zig - zag line ) - sample of silver taken for assaying.
XI is Latin number ‚‚11‚‚ for silver fineness expressed in "dinheiros": 11 (916/1000)

Regards

[Ben.unwin]

Thanks, thats extremely helpful!
I assume the last mark is the maker then? I can't make out what it says IAHA or something