As you are based in South Africa, presumably you have contacted the likes of City Coins and Kaplan to see what has gone through their hands over the years already. As an example reference City Coins, Auction 55, Lot 1, appears to be one that you do not have in your list above:
"- Sir Harry Smith’s Medal for Gallantry named to Thos. Duncan See colour plate (silver; 33,4 mm diam.) Fitted with a plain silver clamp and loosely fitting clip suspender. The medal is in extremely fine condition and has a superb steel blue tone. Part of the characteristic metal flaws, due to the cracking of the original striking, have been removed through neat tooling. obv: A rather Eastern looking lion, be-whiskered and with very curly mane, left, with tail curled above his back, standing on a representation of the veld. above: a wreath of laurel tied with a ribbon. below: in the exergue, the date “1851”. rev: Legend only, above and around the circumference: “PRESENTED BY”; below it, in horizontal lines, “HIS EXCELLENCY” and the recipients name “Thos Duncan” engraved and finally around the lower half of the circumference, “FOR GALLANTRY IN THE FIELD.” The first, and most romantic medal of the South African series. The late Dr Frank Mitchell introduced his original article on this medal, published in the June 1955 edition of the “Africana Notes and News”, and wrote as follows: “Sir Harry Smith’s medal is to the war medal collector what the Cape triangular woodblock errors are to the philatelist or “Burchell’s Travels” to the Africana enthusiast. This medal is purely South African; it is extremely rare; it was the first medal ever worn by South Africa’s fighting men; it illustrates a most interesting period in our national history; and the details of it’s origin, its manufacture and its award are tantalizingly concealed amongst our records of the past. It has, in fact, all the ingredients which are calculated most to tickle the fancy of the discerning collector and to inspire the enthusiasm of the student”. Since then much has been written and speculated about this important and rare award. An illustration even graces the front cover of the most recent edition of Medal News (August 2005). Further details have been presented by Gordon Everson in his classic book “The South Africa 1853 Medal” and his subsequent article published in the September 1983 issue of the “Medal catalogue of the London Stamp Exchange”. However, the intrigue, romance and speculation remains. No medal roll has ever been found. Nor is it likely that all the details pertaining to the award will ever be found. What is undoubtedly factual is that the issue and award of this coveted medal was initiated by the flamboyant Sir Harry Smith, KCB, during his term as Governor of the Cape Colony. Sir Harry directly participated in numerous military field operations during the Frontier Wars of 1847 to 1852 and with all the difficulties he experienced, it is understandable that there were instances where he would have wished to reward his loyal and gallant troops in some way. His epic ride through enemy lines from Fort Cox to King Williamstown in 1851 is most often quoted. Although there was no Royal Warrant nor prior approval of the War Office for the award of this medal granted to local troops, archival records confirm that the full cost of the manufacture of both, the relevant dies as well as the medals themselves, were borne by the British Government of the time. Although he was criticized for his initiative Sir Harry obviously had his way! After it was announced that medals were to be awarded to men of the Levies who had distinguished themselves, the Duke of Newcastle was particularly indignant at the thought that Sir Harry had exceeded his authority. In reply to this criticism, Sir Harry stated, that as he was the Queen’s representative, he deemed himself authorized to grant such a distinction to Local Corps and had therefore “issued a General Order granting medals to those who had nobly and gallantly distinguished themselves, a measure attended with great success”. This medal should also be viewed in context of the then recent awards of both the Naval and Military General Service medals promulgated in 1848/49 (and numerous others) and the omission of a similar award for South Africa (subsequently sanctioned in 1854). As an award for Gallantry it may perhaps be viewed as a precursor to the coveted DCM approved by the Royal Warrant of 1854. An extremely rare and historically important gallantry medal."