Hi - a great looking piece - assume you have a full set of Birmingham hallmarks for 1892, which believe will have date code for Sterling of either r or s, both in lower case.
Shouldn't be too difficult to improve the picture quality by avoiding busy backgrounds of local topography and substituting uniform grey or other dark colour - a large sheet of coloured paper from Lorimer's for example, and you may need to play with lighting to get just the right amount and direction. Do agree though that this is not an easy one to photograph.
Apparently the Stourbridge makers devised a quicker and more economical method to help speed up the process of creating 'the right look' for rock crystal, which involved using a dip mould to create the more obvious larger pillar shapes etc., thus saving much time in cutting the entire depth of pattern on those pieces with a more substantial surface design. This occurred later in the time scale for rock crystal, and can be determined by feeling inside the body. If the dip mould method has been used this can be felt within the body where the patterning of the mould has forced the design to project toward the inside of the piece. Of course if you can't get fingers inside the body then a bit difficult to tell, and I'm not suggesting that yours is one of the later dip-moulded examples - just that it's worth knowing of the existence of such things.
Stuart's and Richardson's were other U.K. creators of rock crystal together with T/Webb and S. & W. which you've already mentioned. Exceedingly little of this stuff gets onto the GMB - it's a tad expensive for members here, and unless you can find the exact match in catalogues, you may not have success in locating a maker.
This one does have the appearance of Rococo - a style from the C18, but presumably still popular even during the art nouveau fashion, which which it shared some similarities. The thinking might have been that if you are going to show off your cutting skills then you might at least borrow a style that was known to be OTT in appearance.
Looking at the Christie's catalogues for the Michael Parkington collection back in the 1990s, he appeared to have very few pieces of rock crystal compared to other glass styles, though that's not to say that his other material which he very generously donated to Broadfild House didn't include rock crystal.
Sorry, I'm clueless about this stuff, but wish you luck in your search - suppose we must assume of British manufacture if only because of the origin of the silverwork
