Good question - truthfully don't know but the series idea doesn't seem to work with the later Stingers, i.e. the 334, 375, 385, and 415. In fact, the first two numbers for length don't work for those boats either - i.e. the 375 and 385 are the exact same boats as far as I can tell. They may have started with the 3rd number being series number, but didn't stick to it. I've seen cases where the model number in the brochures don't seem to match up with model numbers elsewhere.