
We have a Monarch's head, a date letter, London guild mark, lion passant and maker's mark. The maker's mark was the least clear mark but I settled on "B&Mc.D". I hope the image can be of interest and generate comments and more knowledge to confirm or contradict my research.
The "B&McD" does not readily turn up a silversmith from London. However "silvercollection.it" does reference a "B&McD" silversmiths mark belonging to a "Brush and McDonnell" of Sidney, New south Wales, circa 1850's-1860's. There is an accompanying image very closely resembling the image I have posted but with a clearer maker's mark.
The attribution is possibly confirmed as the National Gallery of Australia appear to have 2 examples of "Brush and McDonnell" items. Both are spoons, a Dessert spoon, fiddle pattern c.1850 and a teaspoon, fiddle and shell pattern c.1850. The marking on the spoons is in both cases described as "B&Mc.D /sovereign head /T/ crowned leopard head/lion passant". Samuel Brush and William MacDonnell were the partners but there is variation in the spelling of McDonnell. Brush had until 1850 been in partnership with John Flavelle at Sidney (see Forum link at end). Brush and McDonnell were also known as jewellers, opticians and mathematical instrument makers and retailers of clocks. The Sidney address for them in 1850 was 488 George Street a premises previously occupied by Flavelle and Brush.
Later, at Melbourne, Victoria, a concern with a similar name developed. This second firm at Melbourne originated in the late 1850s when Samuel Brush moved there from Sidney. The 2 firms did run concurrently for a while. The Melbourne address varied, 1858 - 1862 at 26 Collins Street, 1865 -1866 at 99 Collins Street and for 1868 - 1869 at 69 Collins Street. This version of the concern became the Brush & MacDonnell Company (partnership of Samuel Brush and William Drummond) in 1872/73
Below is a composite of Brush & MacDonnell retailed items. Note that the silver mounts to the "Melbourne" emu egg were London hallmarked.

The Forum does have a post relating to the Melbourne firm becoming "William Drummond & Co"(see link).
viewtopic.php?p=65473&hilit=Brush+drumm ... s%20Street
Some sources say this change to Drummond's was because Samuel Brush died, others suggest he just retired, a genealogy site quotes his death was in 1900. Much of the information I have listed was from secondary sources. Odd newspaper adverts can be found on line relating to Brush & MacDonnell though.
Flavelle link
viewtopic.php?p=41803&hilit=Flavelle+br ... %20ROBERTS
Macdonnell link
viewtopic.php?p=63247&hilit=Brush+MacDo ... 20AND%20CO.
Fishless