Legate/Tribune helmet hunt

[caiusbeerquitius]

What characteristic of this type does the Autun example lack?

It does not at all fit into the Apulo-Corinthian classification system, it is neither a "A" "B" "C" or "D" type. Might be a type "E" at best, but doesn´t really fit, since the eyes are not worked out. It´s missing the neck plate at ~90° angle, and it misses the engraved decoration (especially the one in form of animals / boars, sphinges etc. which is to be found on almost all helmets) And it seems to miss the distinctive upper skull section /
(+ eyebrows)
See: Antike Helme p. 107-136.

is pedantic to say the least.

This forum has rules which are there for you as well. Some people need to be reminded continuously, of course, because they are special. Or they think to be so.
Just for you, so that you don´t have to go through all the effort of using the link and finding the right section in the text:

1. No dismissive, hostile, abusive or aggressive negative responses. Malicious behavior (personal insults, "mobbing" or just being a sarcastic thug) is abuse, and moderators will intervene at the first sign of nastiness.