Hi Adrian -
I looked in 50 Years of Collectible Glass last night for that etch and didn't find it. From your pictures it looks like a wild rose. Where have you looked for identification?
Have you tried Replacements, Ltd? I have one of their old books and I will browse through that.
From the other pieces that you have posted, I now gather that you are located in the U.S. It is helpful if you put your location (at least country) in your profile since this is an international board and location often helps narrow down the search for id.
I agree with Christine, that it is likely one of the US Elegant glass makers - Tiffin, Cambridge, Fostoria, etc.