In the discussion of When did the Lord of the Rings take place, there are several suggestions that it might be placed into the equivalent of 1300s England, or 600-700s (based on similarity to "Beowulf and the Nibelung saga as well as the Poetic Edda").
I'll take it as a given that there might not be an exact equivalency between technological development in Middle Earth and that in our own history. However, looking at the movies of the saga, what is the earliest time in our history that technology such as was displayed there was available?
(I'm not talking about CGI, of course. Just things like the siege engines, and explosives, and weaponry. Even stirrups can be dated fairly accurately.)