Officer's shoulder bars - what are they?

Solution 1:

Shoulder bars are symbols of rank worn, as the name implies, on the shoulder.

Here's a page on ebay where someone is selling a WW2 variety: http://www.ebay.com/itm/WWII-US-NAVY-OFFICER-SHOULDER-BARS-/110564952372

Solution 2:

They are called epaulettes.