There is a Ross of London in Loomes, no Christian name-but pre-1755, and the hallmarks on the case say 1768. As to the Son, I would say he came a little later. From what we can see here it looks to be original. The DP for the case maker would be David Pullin. Nice watch
Looking first at the case hallmarks, they appear to be genuine and consistent, with a London assay office mark, (the crowned leopard's head), sterling silver, (the lion passant), a date letter for 1768/9, (the 'N'), and a case maker's mark, ('D•P'), for David Pullin at Coleman Street, London.
The movement signature of Joseph Ross & Sons isn't listed in Britten's, but that's no surprise, because it's most probably for the seller rather than the makers, in common with almost all English watches of the period. Many specialist craftspeople contributed to the making of a watch. The design of the movement is entirely consistent with the case date; a verge fusee with nicely pierced and engraved balance cock and slide plate, (the part carrying the silver regulator disc), and square pillars. The red endstone in the centre of the balance cock may be a later replacement because these were usually a chip of diamond, and the layout of the dial, with vertical hour numerals, is unusual and may also be later, as is the remaining hand. At this time, enamel dials usually had Roman hour numerals and Arabic 5-minute numerals all arranged radially. There are also a few replaced screws, which is fairly common.
Many of these 'memento mori' cases seen today are reproductions or put-together pieces, but this has every appearance of being genuine. Thanks for sharing it.
Here is an entry from the earliest London trade directory that is known to me from 1786 ...
i.e. Rose, Joseph, Son & Co. ironmongers, 17 Foster Lane.
At first sight this may not appear to be relevant. However if you look in Loomes - in addition to the entry Les has noted you will find ...
Rose, Joseph & Son, London (Foster Lane) 1765-1784
Rose Joseph Junior, London 1775-93 Livery Goldsmiths Co.
Rose, Son & PAYNE, London 1790
Unfortunately, there is no indication where Loomes obtained his information.
I suspect that all of these references relate to the same individuals and, given the passage of time, the absence of a Joseph Ross in the 1786 directory and the lack of further information, I would not be at all surprised, that it is their signature that appears on this watch.
Simon - value of watches cannot be discussed on this forum.
Could you possibly post a picture of the other side of the 'lower jaw' of the case, please, the part with the hallmarks on the inside? I'm interested to see how the jawbone part is attached to the lid.
The watch was offered to me by a guy in Poand I have bought from in the past. His English is not good and he asked me if I could identify the maker ( which I couldn't ). He now tells me he has put piece on Chrono 24 if anyone is interested .
My reasoning in asking the question about the way the jaw is attached, was that I suspect that the original watch inner case with its good hallmarks has had the parts of the skull added rather more recently. These pieces often seem to originate from Eastern Europe.
[Edit] Having seen the more detailed pictures, I'm much less convinced of the originality of the case. It's very easy for a skilled worker to take a hallmarked part and incorporate it in a new piece.