Good luck. I tried just that to find out when my YFH-631 flugel left their factory--primarily because I'm curious to know whether or not it has the dreaded "Yamalloy" valves. I was told by one of Yamaha's "Product Marketing Specialists" who responded to my email that they only have serial numbers in their database starting with 1990. I was also told that the 631 started production in 1986, so my flugel must have been manufactured between 1986 and 1989. I wrote back and informed him that the flugel that Chuck Mangione is hugging on the cover of his 1977 album "Feels So Good" is, in fact, a YFH-631. It's a bit disconcerting that the Yamaha factory doesn't know when its own horns were manufactured. How can they handle spare parts or warranty requests? They're a great company otherwise; we have three pro-caliber Yamaha instruments in our home (the aforementioned flugel, plus a Bb Xeno trumpet and an 841 oboe in kingwood) and have been very pleased with their performance and Yamaha's service (the oboe, for example, has 13 pins in its cracked top joint, all of which were installed at no charge within the first five years my daughter owned it, and they have extended the crack warranty to seven years). So, does anyone out there know where I might find a definitive list of Yamaha brass serial numbers? For the record, I'm looking for info on a YFH-631 flugel (rose brass bell) with the serial number 006918A. All I know is that the "A" suffix indicates it was manufactured at Yamaha's Grand Rapids, MI, factory. Any and all advice or info would be most welcome.