This is an altered union suit from Damart.  It's made with a hook-and-loop closure down the front, and not buttons. 

Here's a unique one piece thermal base layer for a man or woman, size Medium.  There's a drop panel on the back "rear".  It's 20" across the front of the chest, without stretching it at all.  It's 55" long (total).  It's in great condition but does have some minor pills inside. 

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