Evidently the 28 showed up fairly early in breechloading cartridge guns. Greener in his work, "The Gun and Its Development", makes mention of the 28 at the London Field Trials of 1879. And as mentioned by others, muzzleloaders--especially flintlocks--were generally made in the smaller gauges and would date well into the 18th century. Economy may have dictated this. I suspect that the smaller bores became less popular as the Arte Of Shooting Flying came into favor. They seem to have experienced a resurgence as sports looked for more challenging tools. Oddly enough my guess is the 12 gauge was the "late comer" in general use, becoming the standard English gauge during the percussion period.
