Quote Originally Posted by Roger Hicks View Post
Half-plate = 4.75 x 6.5 inches = 121 x 165mm rounded to whole numbers.
Thank you - in my research last night I also found there was something called "halfplate" during the first half of the 19th century, which had different dimensions (4.5" x 5.5"). The overall "logic" to the system makes me sometimes laugh, at other times sigh loudly. But given the ease with which one can cut a plate of tin or glass, it's no wonder...