Back in my Buckskinner days when working with Mutton Tallow, I recall reference to it's properties and what made it better than others. I recall that it should come from internal fat or suet as opposed to external fats. Also that it had the highest melting point of any tallow. So, I went looking and found the reference to internal fat but so far, nothing about the higher melting point. ..
Be Safe !!!
Typically, tallow starts with the extraction of suet from a carcass. Suet is hard fat found in the neighborhood of the kidneys and around some other organs. While suet can be used as-is, rendering it removes the impurities and also extends the shelf life. Once suet is rendered, it becomes tallow. As long as it is stored in an airtight container in a cool environment, it can keep for an extended period of time, unlike suet, which will become rancid.