In the Irvin repro thread on the FL there is discussion about the actual sizes of original Irvins. Here is a document issued to the makers with the actual measurements. It is worth pointing out that the measurements found today on original jackets that are the same tagged size from the same maker can vary quite a lot. Shrinking of the jackets over time may be part of the explanation, but I also suspect there was variation when the jackets were produced in the factory as occurred with A2s. Of course some jackets were mislabelled.
