This is a US Navy Officer's Formal (mess dress) Uniform for a Lieutenant (Junior Grade) made  in the style adopted in the early 1900s which initially was used with the fancy  shoulder epaulettes with galloons as used on earlier patterns of Navy uniforms.   The loops to retain the epaulettes are present on the shoulder areas. By WWII however the stylish epaulettes were discontinued from the pattern which otherwise  has remained until this day.    All of the buttons are the proper Pre-WWII style with the Eagle facing to his left and all show  the back mark of "J.R. Gaunt & Son * New York".   Although this uniform does not show either an owner's label or a maker's label, it is possible that  it was made by Gaunt but was unissued as that firm indeed made and sold uniforms as well as buttons.   Were that the case, the sleeve lining wear likely came from non-military (i.e. costume) usage which  is a fate that many former military uniforms have experienced. In any event, the condition is exemplary and the sleeve linings can be repaired. While examples of this pattern of uniform are not uncommon, condition is important and an example in this condition is indeed unique.