LordByron, I'm agreeing with the others here in that this is most certainly of European manufacture, but it might have been done during a period when marking or stamping the guns was not of the same import as it is now. This might predate WW I when there were many fewer gun makers and guessing who made something like this would have been fairly easy. After WW I and especially WW II, European and American economies boomed and anyone with $500 and an idea could start their own company, which is why testing and certification of high-pressure dangerous devices like firearms became more prevalent and they were marked by their manufacturers, testers, certifying agencies and the like.
Many of the older firearms companies that do not currently exist were absorbed by newer companies looking to grow. So unless it's Beretta or some other ancient manufacturer, it might become a real problem with no markings.
Edmund Burke: “The people never give up their liberties but under some delusion.”
– 1784 speech. Taken from Founding Fathers Notes
"In a State of Nature, it is true, that a Man of superior Force may beat or rob me; but then it is true, that I am at full Liberty to defend myself, or make Reprisal by Surprize or by Cunning, or by any other way in which I may be superior to him. But in Political Society ... if I attempt to avenge myself, the whole Force of that Society is ready to complete my Ruin."
-Edmund Burke, A Vindication of Natural Society (1757)
, original spelling and punctuation.