The album contains 42 salt prints and 1 loose albumen print. Seventeen of the prints in the album are initialled MD, and it is from these photographs that the album became known as the Mary Dillwyn Album. The photographs in the album date from ca.1853 and main themes: flower studies, fowl studies, and portraits reflect the interests of the family. The Dillwyn Llewelyns were a cultured family, especially interested in all aspects of scientific endeavour, and the pages of the album offer an insight on the individuals closely connected with intellectual life of south Wales and beyond. In addition there are a small number dealing with everyday life at Penlle'r-gaer, including two evocative images of building a snowman.
The album itself is small in size, 110 x 90 mm. Each photograph has been trimmed and thoughtfully laid down on a page of coloured paper. Inside the front cover it carries the inscription Susan Franklen, Clementstone. Susan Franklen was a crippled niece of Mary Dillwyn's who died in 1860 aged twenty-five. On her death it seems the album passed back to the Dillwyn Llewelyn family.
No other items by Mary Dillwyn to be found in public collections resemble this album in size, content or intimacy. Nor do they possess the undoubted feminine charm of this album. It is known that Mary Dillwyn used a smaller camera than her brother. This had the advantage of using a shorter shutter speed and may be a contributing factor to the intimacy and warmth of her portraits.