(This post was substanically edited/updated on 5/8/14.)
I have a bike frame of unknown lineage.
What is known:
- The serial number under the bottom bracket is IS513786. This fits with the serial numbers for Japanese made Bianchis.
- The frame has Shimano EF rear dropouts that are stamped with 'IJ'. That means they were made in October 1984.
- Although I can't be sure that the fork is original, the steering tube has "Tange.5.I" and a 'J' and 'S' in a circle stamped on it. Also, the crown race was originally JIS sized.
- I got the bare frame, not the complete bike, and the paint is not original.
The dropouts were made in late '84 and we now know that the last two digits of the serial number do not represent the year. (E.g., this '89 Japanese Bianchi has a serial number ending in 86.) So the frame is likely from a '84 or '85 Bianchi (since the dropouts were made late in '84).
FWIW, I've posted pictures below; I've made sure to point out things that could help identify the frame (braze-ons, lug style, etc.). I've tried to arrange the pictures with the most identifying characteristics first.
FWIW, Here is a similar looking, but not identical, 1986 Bianchi Brava. (That Bianchi has the chainstay cable stop on the underside, while my bike has the cable stop on top.)
The bottom of the bottom bracket, including the serial number. Also note that there is a chainstay bridge.
The front of the headtube front. Note that the lugs have points in the middle (unlike some other Japanese lugs from that era).
The Shimano EF rear, drive-side dropout. Note that there are no eyelets. The date stamp is on the back side, so it is not shown.
The top of the seat stay cap has a flat surface and has nothing written on it. (Some bikes, like high end Miyatas, have curved caps and/or the company name cast into the caps.)
The head tube has a pump peg.
EDIT: The whole frame:
The side of the bottom bracket:
The frame's downtube shifter mounts:
The seat stays have a chain hanger. Edit: it's hard to see, but the chainstay cable stop is on top of the chainstay -- not below it.