The Cap on the far right is an officers (as its peaked) & a Field Grade Officer at that (gold piping on the top), but I have never seen one that also has a coloured fabric band below the piping. Looking at the image this fabric band might be in arm of service colour - red for infantry??
Has the museum exhibit got any commentary or can anyone else help?
Am rather interested as I am currently painting WWI Serbs for wargames.