I see what looks like an infantry bugle on his cap. His collar felt-points are so intriguing. It's clear that they say "2" with some sort of design under them,
The collar also displays the bugle sign. Number 2 means the second infantry regiment.
Check this article and watch the attached video explaining the details of Haller`s army uniform. In Polish.
info.kanal6.pl/2021/09/22/blekitny-mundur/