Unfortunately it would appear to be a fake mark - see here, at the foot of the page:
http://www.thepotteries.org/fake/index.htm
'2) There is no known original manufacturer who uses the trade name "IRON WARE" - this appears to be an attempt to imitate the genuine trade names such.' as "IRONSTONE" "STONEWARE"
3) The arms mark appears to be an attempt to reproduce the Royal Arms (but the lion and the unicorn are on the wrong sides) - it was not uncommon for both American and English potters to use a "fake" arms mark.'
