It's hard to tell from the photos (if you could take some more with better light, focus, and a macro lens, to give a better idea of the quality of finish, and maker's marks, that would help a lot), but as has been said, the 16g looks like a generic Belgian gun (most likely made at Liege).
The 12g hammergun is IMO probably a basic Birmingham gun made for a re-seller (Gibson, James, & Co., gun and fishing tackle makers, 49 Jamaica street, Glasgow.).
The best of the lot looks to be the "Dougall and Sons" side-lever gun, which appears to have finer lines and better engraving. If I were to choose one to clean up it would be that one. The maker is probably James Dalziel Dougall of Glasgow and London, a well-established name who produced some very fine guns.
J.D.Dougall. Inventor & Patentee of the Lockfast Breechloading Gun and Rifle. 59 St James Street. Piccadilly. London.SW.
James Dalziel Dougall Snr (1818-91) opened his London Shop ca. 1864. A shop in Glasgow had been open since 1760, until his son opened J D Dougall Gunmakers at Argyle Arcade. Glasgow (1841). His son James, born in 1849, also became a Gunmaker. They died within five years of each other in 1891 & 96 respectively. Another son John was meanwhile running the Scottish Branch at number 23, Gordon Street, Glasgow. Their guns using the Lockfast patent action, were used by many shooters. Later they could add 'Gun and Rifle Manufacturers to the Prince of Wales (King Edward V11) among other Royal family members. J D Dougall jr was the first chairman of the Armourers Club later The Gun Trade Association.
[adapted from:
http://www.lawrences.co.uk/Catalogues/FS100512/page2.html]
More useful information
here
J.D. Dougall & Son. A famous Scottish gunmaker from Glascow patentee of the famous "Lock Fast" action, patent number 1128 of 1860.
"Lefaucheux's fastening system scarcely was durable enough to handle the relatively low pressures that shotguns created much less the substantially greater stresses endemic to rifles. Systems truely stout enough for rifles did not appear until 1859 when Henry Jones patented his T-Fastener and 1860 with the appearance of James Dougall's Lock-Fast action." [Micheal McIntosh, The Big Bore Rifle, page 59]
According to McIntosh, Dougall traded With his father as J. & J. Dougall 1837 to 1841; then as James D. Dougall 1841 to 1891; and finally as J. D. Dougall & Sons 1891 to 1929. His premises were located at 53 Argyle Arcade, Glasgow from 1837 to 1850, at 23 Gordon Street Glasgow from 1850 to 1929; and in London at 59 St James Street, from 1863 to 1883, and at 8 Bennet Street St. James from 1883 to 1893.
The thread cited above also contains photos of a fine Dougall hammer gun, notes that Dougall's ledgers are no longer extant. Approximate serial number dating attributed to a Mr. Keith Woodvine of Mansfield, Nottinghamshire, is offered as follows: 1880 - approx serial no 3780; 1884 - approx serial no 4000; 1892 - approx serial no 4230.
HTH
Mr.G