I certainly don't have the expertise to make the call on this drum with any authority. It wasn't as if congas were totally standardized back then, and the drums didn't (typically) have badges or signatures or any other definitive identifying marks on the drums. My Requena, for instance, has no ID marks at all. And as others have mentioned, sometimes one person might have done the shell and someone else the hardware. That being said, it (the shape, hoops, wood, crown, side plates, and lugs), is certainly is in the style of Gonzalo Vergara, the most famous conga maker of all (and incredibly rare). If it wasn't him who made it, it was somebody very much influenced by him. Almost none of us has ever seen one of his drums up close, though there was at least one board member some years ago that did have first hand experience. Maybe he'll chime in at some point here. Compare the drum picture in this thread with the Vergaras on the following page and you'll see how you have to at least consider the possibility.
http://fidelseyeglasses.blogspot.com/2009/02/tumbadoras-made-by-gonzalo-vergara-cuba.htmlEdit: Just came across a facebook group/page: "Vintage Conga Drums" -- Mark Sanders, who posted the "fidelseyeglasses..." page above comments there, and he is most definitely an expert. Someone re-posted my photo of the drum in question on his page and Mark commented: "Yep, 50's Vergara."
https://www.facebook.com/groups/657966647623440/Wow.
Now I just have to sweet talk this woman into letting go of her sentimental attachment to this drum!