The main device (symbol) in the His blazon is the stag. The main tincture (color) is argent.
Argent is the heraldic metal Silver and is usually shown as very pure white. It is also known more poetically as pearl, moon (or luna) 1Understanding Signs & Symbols – Heraldry, S. Oliver & G. Croton, Quantum, London, 2013, P53. In a sketch or drawing it is represented by plain, unmarked paper 2A Glossary of Terms used in British Heraldry, J.H. Parker, Oxford, 1847, P11.
We should be surprised to find the stag or buck, noble quarry of many a mediaeval hunt, being illustrated in many a coat of arms. 3Boutell’s Heraldry, J.P. Brooke-Little, Warne, (revised Edition) London 1970, P 69. It shares many of the poses to be found with the lion, but also one almost unique to the deer, grazing, as if the animal is still unaware of the hunter’s approach. 4A Glossary of Terms used in British Heraldry, J.H. Parker, Oxford, 1894, Entry:Deer. In common with all symbols related to the hunt we probably need look further for their intended meaning than the pleasure taken by the holder in such pursuits! 5The Symbolisms of Heraldry, W. Cecil Wade, George Redway, London, 1898 P30