They're both listed as Rembrandts on the Rijksmuseum website.
Check out this link and go to portraits. It's what I feel is THE best art site on the web for high quality reproductions. Click on the zoom icon and you can scroll around to see every tiny brushstroke on many, many masterful paintings. Be prepared to spend hours in awe....
http://www.rijksmuseum.nl/asp/framuk...=bezoekersinfo
To find the portraits, click on Collection at the top of the page. Then click on: 1250 Major Exhibits, then Catalogue, then Paintings, then Portraits, then Female. Scroll to the right. It's part of the second grouping of paintings.
The second painting I showed above is listed as a Rembrandt portrait of a Haesje van Cleyburgh, painted in 1634, one year after the Saskia portrait. They do have a very different feel don't they? I'm guessing Rembrandt felt he needed to work the commissioned piece to a higher level of finish than the one of his wife, which he may have done to suit his own tastes.