IIRC, the "assembled in Portugal" didn't begin until the 80s. Not sure what year.
A cut and paste from another forum:
ALL FN/Browning Hi Powers are made in Belgium. However, FN moved its Hi Power assembly to Viana, Portugal in 1980 to take advantage of a new facility and lower labor costs.
So, it you have a Hi Power made later than that it was still made in Belgium, but it was "Assembled in Portugal".
Many others have posted similar opinions, and that's why I think this 1988 Browning stamped Hi-Power is unusual since it is missing the Portugal mark. After researching more, this particular 1988 Hi-Power was probably not made for the US market, and at that time, the Portugal mark was not required. The manufacturer thought it was a US import requirement after 1980.