People, thank-you VERY much for putting your time and effort into this. Here are comments and questions on your particular models:
Cuda2k: Your bicycle is a perfect match with my 1985 specs. However, it could also be 1984 or 1986, for which I don't have specs. Almost certainly not 1987 or later, as it would have had an Accushift derailleur in place of AR and not pre-1984 by virtue of the Inifinity tubing. Most likely it is 1986 based on my current understanding of the serial numbers. Would you mind checking date codes on major components? What is the4 paint scheme? TIA.
Gojohnnygo: SIS indicates 1986 or later. This is the first first Centurion serial number I've seen without alpha caharacters. I do have Accordo specs for 19886, 1987 & 1989, so if you can check the brands and model for the frame, forks, cranks, brakes and hubs, I should be able to narrow down the year. TIA.
Chajmahal: The 1 st Lemans RS is a perfect match with the 1986 model, except for the forks, which were spec'd as CrMo. Interestingly, Mangaloy forks were spec'd for 1987, but the other components had changed. So I'm thinking this is a 1986 model with transition on the forks.
The 2nd LeMans RS may also be a 1986 model, but built in late 1985. I'm basing this on the 1985 specs, which called for SunTour Seven derailleurs. I'd be interested in knowing the paint schemes on these two models. TIA
The red LeMans has components typical of the late 1970s. My guess would be 1977 to 1979. I'm assuming the date codes were 77 and/or 78? Is it all red, or is the headtube a contrasting color? The Cyclone derailleurs seem a bit high end considering a hi-tensile frame and other components. I do have 1979 LeMans specs which are similar to yours, but spec SunTour Vx.
No serial number on the blue LeMans?
Raverson: The components of the earlier Master indicate a 1986 or 1987 model. The 1988 model used the 6400 series Shimano 600 Ultegra, so I'm assuming it was old stock when purchased. Based on the serial number, it's probably 1987.
The latter Master is 1988 or 1989. If it was 1990, it would have been labelled as a Diamondback. We can distinguish 1988 and 1989 based on the paint scheme. Both fade to white, but the 1988 should have a smoke finish (I've seen grey and purple) while a 1989 should have a marble color (I've only seen blue ). Which is it? TIA
AGuinness: Positively a 1987 expert. Shimano 105 SIS made it's debut in 1987 and the 1988 Expert used a fade paint scheme.
Old School: Postively a 1989 Expert. This was the only year to use GPX.
Richardmasoner. Hmm, another alpha free serial number! I've never seen an Accordo with Shimano 105. Fade paint suggest 1988 or 1989, but the 1989 was spec'd with Exage, so 1988 seems the choice by process of elimination.
Dgregory57: I'm willing to tackle the serial number format for any brand, providing the members can supply enough data. The other brands I've been working on are Bianchi, Miyata, Nishiki and Sekine. We already have the codes for many of the big brands such as Raleigh and Schwinn, so I've been placing my emphasis on the more common of the 2nd tier brands.