The two main devices (symbols) in the Jackman blazon are the eagle and per saltire. The two main tinctures (colors) are sable and argent.
Sable, the deep black so often found in Heraldry is believed to named from an animal of the marten family know in the middle ages as a Sabellinœ and noted for its very black fur 1A Glossary of Terms used in British Heraldry, J.H. Parker, Oxford, 1894, Entry:Sable. In engravings, when colors cannot be shown it is represented as closely spaced horizontal and vertical lines, and appropriately is thus the darkest form of hatching, as this method is known 2Boutell’s Heraldry, J.P. Brooke-Little, Warne, (revised Edition) London 1970, P 26. Although it may seem a sombre tone, and does indeed sometimes denote grief, it is more commonly said to represent Constancy 3The Symbolisms of Heraldry, W. Cecil Wade, George Redway, London, 1898 P35.
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) 4Understanding Signs & Symbols – Heraldry, S. Oliver & G. Croton, Quantum, London, 2013, P53. In a sketch or drawing it is represented by plain, unmarked paper 5A Glossary of Terms used in British Heraldry, J.H. Parker, Oxford, 1847, P11.
Where the lion is undisputed king of the animals, the eagle undoubtedly plays the same role in the realm of the birds, its use in this form dating back to at least the Roman period 6A Glossary of Terms used in British Heraldry, J.H. Parker, Oxford, 1894, Entry:Eagle. They tend to be illustrated in quite some detail, especially in continental European arms, and have almost as wide variety of postures and accessories as the lion, well illustrated in the reference 7A Complete Guide to Heraldry, A.C. Fox-Davies, Bonanza (re-print of 1909 Edition), New York, 1978, P235-238 as well as being just the eagle’s head or eagle’s leg. The symbology of the eagle is deep and complex, Wade devotes several pages to the subject 8The Symbolisms of Heraldry, W. Cecil Wade, George Redway, London, 1898 P72-74, but suffice it say that it has long been associated with Empire and those held in high honour – any armiger would be pleased to have any form of Eagle upon their arms!
To add variety and interest to the arms, heraldic artists began to divide the background of the shield into two parts, giving each a different colour. They were named for the ordinary that they most resembled, so the division of the shield by opposing diagonal lines, similar to the ordinary known as the saltire came to be called per saltire 9Understanding Signs & Symbols – Heraldry, S. Oliver & G. Croton, Quantum, London, 2013, P63. Visually rather striking, it became popular and artists added decorative effects to the partition line to distinguish otherwise very similar coats of arms. 10A Glossary of Terms used in British Heraldry, J.H. Parker, Oxford, 1894, Entry:Party.