Learn Italian: Il medesimo formato e l'esemplare coincidono. - The exact same format and the specimen coincide.

medesimo is a direct synonym for stesso (same), but it generally sounds slightly more formal or literary. Placing it before the noun means "the same" (il medesimo formato = the exact same format). If we placed it after the noun (il formato medesimo), the meaning would shift to "the format itself" for emphasis.

Could I replace medesimo with stesso in this sentence?

Yes, but remember that the definite article would have to change. You would say Lo stesso formato... because stesso starts with an s + consonant. Both convey the exact same meaning when placed before the noun.

Does l'esemplare mean "the example"?

Not exactly. While it shares a root with "example", as a noun un esemplare usually translates to a "specimen", a "model", or a "copy" (like a single physical copy of a book or print). In this sentence, it refers to the specific physical item being examined.

How does the verb coincidere work here? Does it only mean "to happen at the same time"?

Just like the English verb "to coincide", coincidere can mean two events happening simultaneously, but it is also widely used in Italian to mean "to match perfectly" or "to overlap exactly in space or shape". Here, it simply means the format and the specimen are identical matches.