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Andreas_Hofer
Guest
Like I mentioned above, the markings are the easiest giveaway.I believe that in the Traditional Latin Mass, the Dalmatic is usually shorter, so the difference between it and the Chasuble can be seen more easily.
An old chasuble had a cross on the back. A dalmatic had what can crudely be described as an “H” - the two lines and a crossbar.
While it’s true that a traditional dalmatic might be shorter, so might a traditional chasuble. The fiddle-backs I’ve seen have sometimes been barely below the waist.