Yes the EO is encased in a diamond shape....is your shell pressed steel or cast steel BB?
Sorry, I'm not sure how to tell the difference between a pressed or cast lug?Unless you know...you don't!
I came across this link a while ago while searching for something else www.bikeforums.net/archive/index.php/t-208881.html
There is a bit of banter between some chaps who used to work and shop in the Birds shops. If I read it correctly(?) it seems to imply that Ken didn't build frames, he just badged up bought in frames. An that Alec practicaly ceased building in late 1976(?). Now IF.. Alec did cease building then, I think it's highly improbable he'd have built with Carlton lugs, whilst Carlton were still trading? Maybe I've got these details wrong tho?
So I'd guess it's either a Carlton with a very unusual frame number. Did most high end Carltons have rivetted on headtube badges, does it have holes? (even if filled you'd probably see signs of this from inside the headtube).
I may have read that..but at work and that ebsite is being censored 'unsuitable'.....so i'll check it when i get home.Yes...Ken was the mechanic and wheelbuilder and Alec the frame builder...i believe they argued a lot.....but if you look at www.hilarystone.com I have seen Alec Bird frames according to HS dating from the 1980s.....and HS generally knows what he is talking about.....still does not explain the Carlton lugs....perhaps something that Dave Marsh will be able to throw some light on when he returns from holiday?I will check for rivet holes this evening after work and report back.Again with the frame number...it is unusual but i once had a Worksop Raleigh 531 Team replica with an unusual frame number....but what if a Carlton framebuilder was doing a 'one off' frame for themselves?....Then sold it on?...or perhaps it was a side line....these are all guesses....but could explain the lugs and if done after Raleigh took over the Worksop site...could explain the fastback seatstays....my Raleigh 531 TR had fastback stays....again a wild guess but plausible......Dave Marsh thinks that is possible.
Or a currently unknown frame built by a small builder, with some older Carlton lugs (which has been mentioned already, but they're 40ish quid on eBay today). This would fit in with an ex-Carlton/Raleigh frame builder..who perhaps bought old stock....or perhaps a not so ex framebuilder??
Maybe I've read your summary incorectly, but is it possible that the Alec Bird connection only came, when Mario Vaz found that was the nearest to a Ken Bird sticker he had in stock at the time?No....the timeline is 1988=Ken Bird decals....but believed to be a Carlton
Then he bought a frame in 2003 with Alec Bird decals, [that the owner of the Ken Bird decaled frame thought was the same but with different decals....Alec B replacing K Bird.....so Mario was replacing like with like......it is possible the KB frame and the AB frame is totally different....however...chap sells a bike with a disctinctive saddle and a frame with Capella lugs that he believes to be an 'old' Carlton frame and buys a frame 10 years later witht the same Capella lugs and the same disctinctive saddle but the frame has been resprayed with Alec Bird decals.......he bought it in 1988 in Bromley close to the KB shop and the bloke he bought it off [different person]...lived in Bromley...Coinicidence? On the balance of probabilities it is the same frame can't prove it as he does not remember the frame number....he just 'feels' its the same.
I feel for your desire to put a name to it tho, I've got a '50s Nervex lugged bike which is similaly frustrating! Good luck!