Hoi Jasper,
I assume you have a lot more 'mileage' than me in these things; this is the first time i see a typical breech loading chamber combined with a lantaka cannon. Maybe this is common to your eyes, but certainly new to me.
Breech loading 'berços' of various sizes were made by Portuguese (and Spanish) for their ships and auxiliary rowing boats, whereas lantakas were made for trade in Asia.
I would always realize that this atypical device was made to
please somebody or anybody, rather than for crude battle
... one of the peas in a pot
