Hello Jeff,
Just found your post and this forum. Your first snake is the style that is most popular on Canadian snake buckled belts of the Oliver pattern, as another member wrote, used by Canadian troops during the Boer War and later belts worn by Canadian units in WW1. This style was also used during the American Civil War, but it was a less common pattern. Most of the this pattern buckle offered as American Civil War are really the post Civil War pieces of Canadian origin. I refer to this variety as the tri-foliate variety - notice the three fingers or digits that extend from the center band. The keepers on this style snake sometimes have extended rather than overlapping connector loops. Let me explain that there are two parts to each keeper - the loop through which the belt loops and the horizontally mounted ring through which the snake links. This ring normally overlaps the vertical belt loop on most keepers, but many of the Canadian buckles feature an extended ring that is attached to the side of the belt loop rather than directly overlapping it. I hope this makes sense. Then again, your examples also include bent ring keepers with and without sliders to cover the unbraised ends - as for as brass wire keepers, but iron and steel keepers are also used and many are gilded or silver washed or plated with nickel, tin and later chromed. Luckily, the keepers are not as complex a subtopic as the snake patterns!
Snake buckles were used by and in most of the former British Colonies - as in America, Australia, Canada, Hong Kong, and New Zealand. Their use extends in an almost unbroken series back to Tudor period - on sword belts, as seen in period paintings. A few styles extend over generations of users, but differences are recognizable to distinguish individual makers, but identifying makers would be a near impossible task through time. I am not aware of much extensive literature on snake buckles, but I have amassed 215 examples and a few score of images of soldiers and others sporting snake buckles - for a book. Probably a series of books, starting with an introductory text.
Your last snake looks more like the type of pattern used by freemasons to fasten their aprons - an extremely specialized branch of snake buckle use that was largely secretive until recently. The Masonic snakes are usually smaller and mounted on smaller and thinner wire keepers than those employed by the military.
British police have also utilized snakes as well as Hong Kong police, Royal Canadian and their predecessors the Northwest Mounted police of Canada. Australian and New Zealand police also have used snake buckles in the past. The RUC (Royal Ulster Constabulary) and the earlier RIC force used snake buckles up into the 1970s.
There is another whole major branch of snake buckles that use what I term plate keepers rather than wire keepers. The most familiar example is the lions head keepers used by Cavalry units. The French have extended the use of many different plate types including medusa heads and various symbols, such as horns, stars, quarter moons, etc. The French use extends from the Napoleonic period to at least pre-WWII.