Apologies for not responding sooner – I have been rather ill.
You have the smallest of the Ripple vases (swung vases are classified by base size – yours is the smallest at 2.5 inches). Ripple was one of the first Imperial items imported into the UK, from 1911 (advertised in the Pottery Gazette).
I have to disagree with James regarding what collectors call this colour. Carnival collectors are very particular when it comes to even subtle colour variations. They do not call this colour “green” – they call it Helios. It is a very specific iridescent effect, although I will also point out that it isn’t an especially popular colour.
Glen