ok, I have an update for the Grover and Grover comments (my underlining in Christine's quote below)
CH British Glass 1800-1914 (2009) says of S&W
Dolce Relievo was introduced in 1884. (see post earlier for the full paragraph where there is no description of the background of the pieces at that point)
He goes on to say later in that section
'Engraving skills developed on rock crystal glass were often transferred to cameo decoration. One specific technique was the chipped, hammered or 'pecked' background which appears as a frosted or cracked surface. Production was low because it involved chipping the glass against a rotating S-shaped metal tool, fixed on teh end of a spindle and set in an engraving lathe. In the Stevens and Williams books this decoration, patented as a 'chiselled' ground, first appears as pattern 12981 on 24 September 1887(Colour Plate 18)'
'According to Grover and Grover talking about Stevens and Williams in English Cameo Glass "Dolce Relievo was the soft sounding name given to beautiful vases with an ivory coloured body and an outer casing of different colours, generally light purple or cream. They were decorated in low relief by the various etchers. Coloured casings were used on light backgrounds, with the ground 'peckled' or 'chipped' and the design in relief in colour. Silver mounts were used on many pieces, done by silversmiths of Sheffield or Birmingham."'
So, from CH's book it is seen that Dolce Relievo pieces without the peckled/pecked backgrounds were produced between 1884 and 1887.
No update on the colour yet.