Yeah that's the Butterworth Brothers we are talking about. They specialised in scientific and industrial glass but as the other Manchester companies shut down, they bought up Burtles Tate and their workforce and did some simple fancy glass. The napkin rings come in 5 varieties that we know of; plain, red cased, blue cased, red cased with white inside cased, blue cased with white inside cased. We've identified 4 patterns to date - that circular one and three other general foliage. That may be the extent of their range.