Tim, you don't have to think about where the feet have been and troden, in the recipe you mention salt, this was no doubt to extract as much water as possible from the trotter and ears then they would hot fry them till almost crisp. If you remember cows hooves were the prime ingredient of glue, and the jelatine and jelly fravoured with strawberry, came from pigs trotters and the like.
I can remember mother boiling pigs trotter, its only after they had been simmering for an hour that you skim off the scum and froth off the top, then continue simmering until the skin and bones can be lifted out clean leaving the flesh in the stock, when all the veg ( that pigs eat) was put in( the same with rabbit pie you include all veg that rabbits eat) simmer again until the vegetables are cooked and serve, it is the most tender of meat that melts in your mouth.
With the pigs head, that was done the same the most meat was on the cheeks, boil then skim, then simmer again until the flesh is left in the pot after lifting out the bones and skin eyes and hairy ears.
This was again reduced by simmering until the stock is noticeably thicker, all the flesh was ladled into big basins, then the stock poured in enough to cover it all, a plate or saucer what ever was a good fit to the basin was placed on each basin and a weight was applied to hold it down firm. They were taken into the pantry and left to go cold, the stock then set like a jelly. The jelly round the edge of the saucer set and formed a seal excluding all the air.
After a couple of days mother would turn one out onto a plate and slice it for sandwiches or slices on the plate along with salads as you would with ham, but this was called BRAWN. The other basins as I recall kept quite well in the winter time in the cool of the pantry ( no use by date in them days) for up to a month. It was a treat that we always looked forward to.
I know one time the butches used to make brawn and sell it sliced over the counter, when we ran out occasionally mother would reluctantly buy some in and moan like hell about what he charged.
Boveril, I remember al the old thin cows that went through Uttoxeter market were cooked and sqeezed out hard to make Bovril at Burton on Trent