There's a double page spread in Ray. Notley's 'Popular Glass of the 19th & 20th Centuries' - pp. 48 - 49, covering commemorative & souvenir wares, and none of the pieces he shows are indicated as having been Registered, so seems manufacturers weren't too bothered about protecting the designs of these things. Perhaps it wasn't thought of as 'seemly' to Register something depicting the Monarch.

A couple of the items shown incorporate photographs - one is a milk-glass plate/frame with what Notely says is a 'fused' photograph of Ed. VII - either dark-room printed or an invisibly-glued, specially glazed print - looks to be a sepia tinted or b. & w. photograph. Maker unknown apparently, but presumably someone thought enough of the process such that it was patented on 20.08.1901 - marked on the glass to this effect - this confirms Kevin's thoughts about patent protection of this process.
Quoting Raymond Notley, he writes ............... "Davidson at Gateshead developed a steady business in photographic souvenir ware, which was typified by the photographically-derived, reverse-transfer print. Affixed to the back of the glass the print was translucent yet reasonably waterproof. Blue Opaline was the favoured colour, and the same 'frame' can be found depicting various resorts, as well as pictures of Queen Victoria ................... etc. " Notley gives a date range for these plates of c. 1895 - 1910 - a little beyond the Golden Jubilee date on the op's item.
Despite the implication of Notely's comment that "Davidson - steady business etc. etc." - these Davidson Pearline items with photos seem somewhat uncommon. Although I don't now own any Pearline, I seem to recall that both the yellow and blue forms were all marked with a Registration No. - does that sound correct?
small pw. are known quite commonly with paper photos of seaside resorts and similar pix, from c. 1880 onwards.