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Muscle cuirasses were rigid and rather uncomfortable; they also required custom fitting. So did lorica segmentata, but it was far more practical in battle. It's hard to say for sure whether the muscle cuirass was seriously used in battle by the Romans, but certainly it was exclusive to particular officers, such as a legate. They are very common in depictions,as it was a classic piece of armour and so you can imagine it was mainly a glorified status symbol. I know this doesn't really answer your question of how late, but this gives you a background. You might say that they were outdated long before, but were used to make showy officers.