The placing of this Registration into CLASS IV is intriguing - did Sowerby suddenly become paranoid around this time?
If you look at the Representations Books at The National Archives at Kew - the repositories for all of the images submitted to the U.K. Board of Trade during the lozenge years of 1842 until very early 1884, it does appear that during those years all of the drawings, from Sowerby, carry the designation CLASS III written clearly on the drawing - which is what you'd expect to see, since CLASS III was specifically for glass only.
However, Registration 4833 (April 1884) is a very early 'post lozenge' period design, and from February 1884 the system of allocating Nos. had changed - the CLASS system remained, but Rd. Nos. for ALL of the thirteen ornamental Classes were allocated from a single series of consecutive Nos. ... looking in the books you can find a piece of glass numbered like this example, and then no more glass Registrations for another hundred or so numbers, or more. Some of the Representations books in the closing years of the C19 are filled with reams and reams of designs for lace, clothing material, wallpaper etc. etc., which can make searching for glass a tedious business sometimes.
All of which is doubtless boring for most folk, and it was a long winded way of saying that until 1884 Sowerby seem always to have kept to the system of showing their glass designs as CLASS III, but post February 1884 may have become more devious as to recording their submission correctly, and just might have used CLASS IV to mask the whereabouts of their designs.
I know we've discussed previously many glass Registrations that should obviously have be included in CLASS III, but which for whatever reason end up in CLASS IV. Are we aware of any Registrations incorrectly CLASSED prior to February 1884, or are all of those we've discussed over the years dated post February 1884, when the systems had changed??
Anyway, here is a picture of both parts of Anne's comport - courtesy of the Trustees and Directors of The National Archives at Kew - for which continued thanks as always. You'll notice that there is no mention of this item consisting of two parts.
The National Archives Representations reference is BT 50/8.