Peters referred to that bullet as belted, it was common 80 years ago, in many cartridges. Peters was "Rustless" or non corrosive when this load was produced. Not sure what the year of introduction was for the 300 H&H belted 225 gr load, but you can dig thru the old catalogs here and find out. Looked at the 1939 catalog and it was present, can track back earlier probably. Before the 300 Win Mag was introduced, the 300 H&H was sometimes marked 300 Mag.
For some reason cannot get the general page address to copy over, use the above address cut off, before the 1939.
Like these old catalogs, as I like to load those old hollow points when I can find them, catalogs describe their intended performance.