I bought 2 paintings by Giovanni Boldini,The Black sash and Portrait of Mrs Howard Johnson?

They look like real paintings and both are signed on the lower left corner in black paint (hard to see but can) and The Black Sash one is dated 1906 in same black painted signature.I bought them in a antique store who purchased them from a estate sale.I live in Kennett Square,PA and was told was out of a house around the area of Unionville,PA....Does anyone know of these? How to really tell if a real painting? They are in very nice frames with the paper backing so I can`t look at the actual back.