really! "mid-fifties"?? do you think that's likely given the details (like Campy forged DOs) and the decals? Unless it's a repaint, it sure seems later than mid-'50s to me...

This sounds very suspicious to me. Your frame number sits right in the 70s triangle frame puddle; they must have built a crapload of mixtes in the 50s to get to 11000+, or else their serial numbers are assigned by a random generator!

I think the Reynolds guy was being lazy or didnt want to be bothered with a mundane inquiry or misread my serial number or fat fingered the key board. Mine has the 'Reynolds Tube Co Ltd" decal so it would be '73-ish to '77-ish.

It is not my intention to make a plug for my Bob Jackson frame on Ebay... I am the second owner of a frame numbered 10046 and I was told by the original owner that he bought the bike in the early 70's.

There are lots of photos on my listing if you want to take a look:

http://cgi.ebay.com/ws/eBayISAPI.dll...STRK:MESELX:IT

Original owner had braze ons put on. Bike has been re-painted and there are no stickers on the frame.

My frame/fork looks identical to this other frame on bikeforums numbered 13473:

http://www.bikeforums.net/showthread.php?t=437580

Having worked for a shop that sold Bob Jackson frames in the 70's visually it could be 1972 to 1974.
They were cranking them out, (I think they must have subbed some too) in 1975 Bikecology in Santa Monica bought a big load of them and we stopped ordering.
My suggestion is to be careful and inspect the bottom bracket as it goes together if you use a typical period assembly, the shells were often distorted, the shell faces were not parallel and a cup would seat but not perpendicular to the spindle. If that is a problem then using a Phil Wood BB or similar will solve the problem.

http://www.flickr.com/photos/2816407...th/4977338047/
I bought this tandem last week. s/n 15309. As far as I can tell, it is from around 1980. Since Unworthy1 has 15305, I thought it might be fun to compare two bikes only 4 digits apart.

Bob Jackson Block Decals 15824 build date June 1982
 

Bob Jackson Block Decals 15824 build date June 1982

I was surprised at the request, as I've owned two Bob Jackson's, and they were excellent with providing me the date information when I inquired. Sounds like a really nice machine.

The serial number on mine is 6832. I guessed around 1970, the Bob Jackson factory said Quote..." such an old frame I have no idea on that one" . I'll be interested to see if anyone can shed more light on it's actual age.

I know this is an old thread but will add my knowledge of my current BJ.
Serial 9227 shipped to original owner at Offutt Air Force Base, July 1972. I have the original BoL with the dates.
https://cimg0.ibsrv.net/gimg/bikefor...89e8ba378b.jpg

Another Bob Jackson serial number.
 

Another Bob Jackson here. After a few hours scouring off rust it looks to have the serial: 20543

I have no idea when it was built. From what I am seeing with other serials posted it should be late 80's or early 90's.

https://cimg2.ibsrv.net/gimg/bikefor...38d3f2e71f.jpg

https://cimg1.ibsrv.net/gimg/bikefor...52b533f417.jpg
https://cimg5.ibsrv.net/gimg/bikefor...3a0cb54d54.jpg

So I am curious about how these serial numbers work... serial 1248 on mine. I know my bike is at least 1976 or older, as my friend bought it used that year. Any thoughts?

Thread resurrection time!
I've just bought a frame as a runaround, but it's pretty nice, possibly better than my Mercians! it is actually very Mercian like though.
The frame number is 11078 and at a guess I'd say its very early 80's.
It has been resprayed by Barrons in the mid plus 80s.
It's 531. 100/125 OLN. 68mm BB. 27.2 post. Gear cable guides are on top of BB shell. Campagnolo horizontal drop outs, the shorter type. 1 set of bottle bosses. Braze on D/T shifters.
Drillings for hex bolt mount calipers. And the frame is close mudguard clearance.
I just need to upload some images.
A Jackson ?

I can't post images until I've posted a few more times.