No, I meant to say fit. My error
I say the present tense might be better in modern English and reflect better the sense in Latin. Note that an older translation may use “has been made” rather than “was made” to convey the sense of “present perfect” in English.
First, “has been made” is not conveying the sense of the present perfect. “Has been made” is a perfect passive in english.
The problem here is that latin does not distinguish between a simple past and a perfect. The perfect is a past action. It can be translated as an english perfect or simple past, and this depends not only on context but also to a large degree on the translator’s choice.
In other words, conveying the sense of the english perfect is often an incorrect translation, because english, (like greek) makes a distinction which latin does not. Its like the continous present in english (he is making). I have yet to come across a language which has this as a present tense. So translating present tense verbs from latin, greek, german, or french is made more difficult because english often uses the continous present.
How do you know that (“This isn’t one of them” & “more natural not only for latin but also in english”), or what evidence have you for that?
First let’s go back to the options. Either facta est is a perfect passive, in which case it should not be translated with “is,” (which is present not past) or it is a predicate adjective + copula, in which case facta is simply an adjective (not a periphrastic with est) and “is” is correct, because in this case est is the only verb, and it is present (as opposed to be part of a verbal periphrastic construction).
One reason facta should not be read as an adjective is pretty simple. Adjectives are descriptive in particular ways, and certain verbs lend themselves to such uses. For example, “divided” is easily read as an adjective. Likewise, “the door is closed,” “His head was turned,” the painting was colored" and so forth all use verbs as adjectives (participles). This is because they are describing what is or could be a state or aspect of something.
“to make” does not lend itself to adjectival use. “Made” is a one time occurance the results of which are permanent (barring destruction). “Made” is not descriptive in the way “colored” or “divided” is. It is in all forms an action. In the sentence “the book is colored” the adjective colored describes the book. However, in “the chain is made” made doesn’t describe the chain (it isn’t really a quality or aspect of the chain the way that colored is of a book); rather, the passive “is made” describes an EVENT (which makes it a verb). So it doesn’t work well as a predicate adjective. This reading is strengthened by the PP “out of iron.” The prepositional phrase is adverbial in that it describes the PROCESS (a verbal element) of making.
“What does the book look like?” “It is colored.” Colored describes the book.
“What is the book made out of?” “The book is made out of paper.” “out of paper” is a description of how the book was made (an action). Adverbs describe the “how” of actions, not adjectives.
Also, this copula+ predicate adjective is where the passive construction came from. See, e.g. Allen & Greenough 495: "From this predicate use arises the compound tenses of the passive,- the participle of completed action with the incomplete tenses of esse developing the idea of past time: as, interfectus est, he was, (or has been) killed.
Moreover, it is far less common for the perfect participle to carry present meaning (which is why there is a present participle). The same is true for the perfect in general.
Finally, the ex ferro is akin to an agent of a passive construction, forcing a passive reading rather than a predicate adjective reading.