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Welcome to
SGW, Dave ! !
You don't have an O/U shotgun, you have what's commonly referred to as a "combination gun".
European/Italian made firearms should have a bunch of proof marks stamped in hidden areas, like the barrel sides/undersides, the frame/receiver, etc - that are only visible after the barrels are dismounted from the receiver.
The various marks indicate things like the chambering(s), the loads, the date of manufacture, and usually a maker's mark - to name just a little of the info.
If you will post some clear/close pics (w/o glare) of the proof marks, there's several experts here who may be able to assist you inquiry.
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