The various IOR "ton" classes were just boats that rated the same under the IOR Rule. It's really just a prediction of speed potential. Many different designs built by different manufacturers could be rated as "quarter ton" or "half ton" or "one ton". Not sure what the numbers were for each rating.
Yeah it's the "numbers" I am looking for. I was thinking there would have been some standard criteria to which all boats in the class must have been built to.