Regarding Steed, I recall Despos has mentioned that Steed rotates the arm seam quite forward.
You can see it on Andy57's suit here.
You can also see it on my Steed coat here.
This detail seems quite distinctive. The arm seam is not typically so forward that it is clearly visible from the front. I don't know if there is a technical reason or part of the house style. Just a tit bit to help identify Steed suits.