The visible Assay Office mark could be that of Porto — for reason of is struck on a circular surface, the invisible parts of cartouches border could be interpreted only. But I guess its Porto.
It’s not as stated to be the 800 fineness mark for Gold, which was in force from 1938-1984! These marks have their indication numerals above a tower (maybe an interpretation of the famous Â»BelenÂ« tower in Lisbon?). (Source: vol. II, p. 22, nr. 153)
On the here visible mark is the 8 in the lower left corner = that’s the new mark for Gold, in force from 1 January 1985 on. The symbol above the numerals 800 is a portrait in profile of a left side looking stag with antlers.
So we have a fix point of time frame: Assayed after 1 January 1985. (Source: vol. II, p. 420, nr. 4093)
800 of fineness in Gold signification is that it is 19.2 carat.
As already mentioned, my interpretation of Assay Office is to be Porto.
But that hasn’t withheld me to look trough all mark examples of maker’s mark — because it could be also Lisbon?
Portugal has, from 1887 on, one of the trickiest maker’s mark systems in the whole “Western” hemisphere. There was only constancy: First letter of first name (or company’s main names) has to be included! Letter type could be Antique, or Grotesque (the almost preferred one), or Free style like e.g. Script.
The form of cartouche was, and still is free of choice — not to speak from the contents of this stage: It could be e.g. a symbolization of a tramway, and the entrance frame is a letter D.
In your case, the maker’s mark looks like to be simple = yes, the cartouches contour is well incomplete. But the “stage” seems to be filled up very simple too = with a kind of an upside down adjustable circle — and between his shanks a letter type. But which letter type?
The capital letter types height could be 1 mm only — a bad struck could become collector’s nightmare!
First I’ve searched for P; then after for B, for R — no match at all. Well, I’ve searched from 1887 on — because some signs could have beheld function for successors too?
Source: Â«Marcas de Contrastes e Ourives PortuguesesÂ» ISBN 972-27-0773-6. Vol. II (1887-1993). Reprint 3rd ed. 1997, Lisbon.
Solution is maybe, that you write a request to Porto’s Assay Office — I think so, it could be in English.
Kind regards silverport