The 375 veloplex is the first commercial belted case I know of. It was developed around 1910 by H&H and was a miserable failure. Only marginally more powerful than the 9.5's already on the market. It begat the 375 H&H in 1912 one of the greatest cartridges ever.

I thought another of the theories behind the belt was so single and double rifles made for rimmed cartridges could be adapted with minor extractor modifications. Might be more gun loony legend though.

"When you disarm the people, you commence to offend them and show that you distrust them either through cowardice or lack of confidence, and both of these opinions generate hatred." Niccolo Machiavelli