Found one more tidbit.....that might help with dating. Info below taken from this link
http://www.bushywood.com/bricks.htm:
For centuries bricks were moulded by hand in wooden moulds. These were four sided and rectangular in shape with no base or lid. Moulds were placed either directly on the ground or on a roughly made brickmakers table. Bricks made on the ground are generally pre 19th cent.
They were known as 'place' bricks and often contain grass impressions.
From the 19th cent rectangular block of wood, smaller than the mould dimensions, would be screwed on the table which created the brick's 'frog'. Sometimes letters were carved in the frog to identify the brickyard owner.
DATING BRICKS
Bricks which form all or part of a building may have their date fixed by the history of the building. Loose bricks with a maker's mark in the frog can often be dated if the brickmaker is identified. Bricks without these guides are difficult to date with any precision. With a few exceptions, raw materials and firing temperatures have remained the much same for hundreds of years. What pointers there are merely typify a particular period, rather than confirm it.
Brick Dimensions
Brick size is often used as a guide to the general period in which they were made. In the course of time bricks have evolved through different dimensions, the most crucial dimension being thickness. Time has seen a gradual increase in the thickness of bricks but trends may have existed in some regions longer than others or even coexisted within the same district.
On the Isle of Wight the earliest known bricks, of the 16th century, are generally around 1 3/4in (4.45cm) thick. There were increases in size towards the end of the 18th century to 2 1/4in ( 5.7cm), although there is little Island evidence of changes as a direct result of the 1784 brick tax. Thereafter gradual size increases throughout the 19th century met, and sometimes exceeded, the modern standard thickness of 2 5/8in (6.3cm). These are only general guidelines and there may be plenty of buildings which demonstrate exceptions, particularly if the bricks were imported.