I most definitely did NOT know that - thanks for filling me in! All these years I thought it was the day (but I'm also a gear ignoramous). Being a Jazzmaster, not a Jaguar, I looked up the number guide from another board. Apparently 1968 Jazzmasters are 19 and Jags are 15 as you said. So either the instrument was misnumbered, unlikely as one is long-scale and one is short, or far more likely, I misremembered. Either way - 15 or 19 - is still about 3 weeks after I was born, so that didn't change.