Hi,
Interestingly Brazil's historical connections with Portugal , might explain why a Brazillian piece ended up there .....or ...if not from Brazil, could indicate that, indeed, this is very old and shows the influences that pre-date the materialised on Brazillian 'pieces'.
However, as already stated 'lined designs used as decoration are found in many cultures, countries and 'time periods' and may be difficult to ID.
Fernando, as I said before I have a doubt this is African but, historically Portugal and Brazil were involved in the 'slave trade' and it is quite possible that your item was influenced or made by an African culture.
My main 'doubt' that this is African is the fact that the 'point' is offset from the socket. All African ones I have seen have the 'point' centrally placed.
A Mystery
Regards David