i recently picked up a miyata 615 on ebay. i've been told it may be an early 90's model, actually, so may not fit in this thread--it has a 6 speed cassette (18sp altogether), and downtube shifters. i haven't toured on it, but i commute 20 miles roundtrip to work on it, and i really enjoy the ride (much more than the trip on my previous bike, an early 80's le tour). it's triple-butted cromoly frame, the same as the 1000's, but maybe cheaper components. i was curious about it's history, tho'. i see lots of 610's and 1000's, but this is the only 615 i've come across. i've heard that bike manufacturers sometimes add a new or modified line of bikes in a production year, and so these bikes often come in under the radar, so to speak, and/or are maybe not produced in the same quantities. did miyata decide to upgrade/modify the 610 in mid-"season"? or is the 615 a branch in the evolution of miyata bikes?