The old pocket watch pictured below came to me by way of my grandfather and I suspect to him from a great aunt. It's seen some things ... Unfortunately, none of its previous owners are with us any more. I've been trying to learn something about its origins, so I began looking into the interesting world of hallmarks using resources such as silvermakersmarks.co.uk, hallmarkwiki.com, and 925-1000.com. The hallmarks on the inside of the caseback can be seen in the second photo below. Some I have been able to decode, some not.

With apologies in advance to those more knowledgeable than I, here's what I think I've learnt and what I still don't know: From what I've read, the lion passant (top centre) indicates that the watch case is made of sterling silver (92.5% purity). Apparently, each sterling silver piece should have four marks: (1) the lion passant, (2) a city mark indicating where the item was assayed, (3) a date letter indicating the year it was assayed, and (4) a maker's or sponsor's mark indicating who sent the item to the assay office. Each of these four marks can be seen here. The city mark in this case is the mark of the city of Chester, UK; shown on the left as three wheat sheafs and a sword. Each assay office used a different series of letters to record the year. Letters were re-used over and over in a different way in each city. So in order to decode the year accurately, one needs to note not only the city and the letter, but also the font and the shape of the shield around the letter. This is where a little bit of mystery starts to sneak in. The Chester date chart from 925-1000.com is shown below.

To my eye, the stamp on the watch could match either the mark for 1816 or that for 1838. Another mystery pops up in relation to the maker's/sponsor's mark (the series of letters in the centre). While there are online lists of these by city, I've run into two problems. The first is that it's difficult to actually make out the initials in the mark. My best guess is that the mark reads "ILS&Co", but I would not bet my house on it. The second problem is that I've not found any record of an ILS&Co or any image of a Chester maker's mark that looks similar to this in the online resources I've consulted. So, while I think I've traced this watch to a particular city of origin, the date of manufacture and maker remain something of a mystery.
There are also two sets of letters/numbers and what appears to be a serial number on the inside of the caseback that I have no clue about. The serial number can be seen in the centre of the photo above. The other marks (bottom left and right) seem to read: R^5031RF or RA5031RF and X3372M. Possibly made during servicing?
A couple of other things that have me scratching my head about this watch can be seen in the picture below. First, it appears that in order to get a look at the movement, one would have to remove the hands by unscrewing the small, square screw, then remove the dial and go in from the front. The case back does not appear to open or be be removable. I am not going to attempt this. Second, there are two small switches or levers at about 6-o'clock and 7-o'clock. I don't know what these are for and of course I do not want to fiddle with them given the unknown condition of the internals.
Apart from what I have discovered above, I am utterly clueless about these old pieces. This has become a fun little project and I find the watch endearing so I will continue digging. I'd be interested and most grateful for any leads or to hear any thoughts from members who have more experience with these pieces. Cheers!