The knives are interesting to look at; but I don't expect there were ever anything similar to these used for the purpose they are insinuated. The saw would put way too much pressure on the roosters leg and the seam ripper would never fit in the intended seam. I have seen historic models that appear similar - just not sure they were made for the actual use by someone that understood the function.
As to the cruelty aspect, it is a human continuance of a natural character. Animals fight in nature, many times to the death. Roosters will naturally grow long, sharp spurs. Even yellow leghorns will annihilate their own clutch mates when a good hard rain changes their appearance just a bit. But if I were born a rooster - I would much rather live 2-3 years pampered in a pen or on a tie string with hens wondering by every once in a while than coming out of the millions of eggs a year that supply our food industry via Tyson chicken farms, etc.. Three good months with about 6 square inches of your own space and then have your throat slit for little Billie's nuggets. Might even have a chance, even if it were 1 in 100, that I could spend my life in a brood-pen. Chickens are not taught to fight, just like children are not taught to sin - it is our nature that makes us do the things we do. Having humans affix spurs to shorten the battle for the most accurate bird does ruin the natural argument; but in the barnyard, many times these fights will last more than a day. I have always wondered why people don't capture queen bees to fight? There is a murder every few weeks in a hive anyway; seems like there would be those that would try to profit off such violence in nature anywhere they can.
It is curious to me why a person would be perfectly happy with eating veal, yet chastise someone from a completely different upbringing for doing something their family has done for generations. There are countries which nearly the entire population takes pride in the gamefowl industry. I'm not moving there; but I'm not going to tell them how evil they are when I see the murder rate in Chicago over most weekends or the number of babies we terminate each year. So, we elect officials that pass laws to remove these actions of society we don't approve; but sadly there is no way yet to pass our personal virtues to the population (thank God).
BTW, why is this knife even posted here - IT HAS SCREWS HOLDING THE SLABS ON