Hello and welcome to the board. We have a few topics here on Heron Glass (the Search function in the top menu will find them if you just put Heron into the search box), but to get you started here is one: http://www.glassmessages.com/index.php/topic,26308.0.html
- one of the replies is by the daughter of Heron Glass's founder. Heron started in the early 1990s in Cumbria, England, and closed down a few years ago. Several of us have a few of their items. I've not seen one with an acid stamp but anything is possible and others may have seen them too.