The Havilland & Gunn rifle and the Gem rifles, while similar in action and appearance, are literally generations apart. The H&G is the first of the species dating back to around 1865 or so. They were never commercially successful. H&G then sold the rights to H.M. Quackenbush (late 1800s, early 1900s)who did manage to make the design a commercial success. Quackenbush later (still early 1900s) sold the design to European manufacturers who began building them there. One manufacturer used the trademark "Gem", and it somehow over the course of time became the buzz word normally associated with this particular action. The "Gem" rifles were made by a number of manufacturers, so it would probably help your search if you had some info in regard to the specific manufacturer of this engraved version. To my knowledge, none of the H&G guns were factory engraved.
A very early Havilland & Gunn with a two digit S/N.