Not sealed. No AF. Not truly internally focusing -- the front element does stay behind the filter ring at all times, but it does move front to back (like the 50L). It certainly is a path of ingress without a filter in place.
For the f/1.2 obsessed, why not get the 50L? On refurb, it's $950ish and you get sealing, AF and a much more compact design.
For the sharpness obsessed, surely get the Sigma 50 Art. Flaky AF still crushes no AF for general use.
Glad to see Samyang making moves, though.
- A