The undress frock of a lieutenant was a working garment. It is of blue wool and has a very low collar lined with white velvet. The frock features wide lapels buttoned back with buttons of horn faced with brass that has been die-stamped with a Tudor Rose motif. Just inside and running the length of both lapels is a second set of buttons and buttonholes worked on white linen/wool twill. In this way the coat could be buttoned closed without unbuttoning the lapels.

In keeping with the styles of the mid-18th century, the coat has extremely full skirts, three point pocket flaps and faux buttonholes on either side of the central back vent. The sleeves have boot cuffs that are fixed with buttons and lined with white shaloon, a linen/wool fabric.