I would agree, almost certainly Stuart's 'Stratford Rings' pattern. Have a look on the Board's 'Search' - should be awash with various shapes showing this pattern. Sometimes have the Rd. No. on the base too, but they weren't always marked unfortunately.
Green probably the most common colour, but also in amber and blue, plus clear of course - as pix attached.
Maybe this one is worn and backstamp now very faint, perhaps - not always on underside of foot - could be on the edge of foot rim.
Design started life in 1921 and went on until 1970s, apparently................. Stuart didn't do a uranium green though - at least no in this pattern.