Complex sentence: The closest surviving Imperial Roman helmet to the type illustrated in relief sculpture (illustrated) is from the 2nd century AD, found in Bavaria, and has been classified as a "pseudo-attic helmet" by some scholars.
Split into simpler sentences: The closest surviving Imperial Roman helmet to the type illustrated in relief sculpture (illustrated) is from the 2nd century AD, and was found in Bavaria. It has been classified as a "pseudo-attic" helmet by some scholars.