During my Royal Enfield WD models research I have found several WD/C and WD/CO engines with a "B" or a "BB" stamp close to the oil filler cap. I had always thought that this was some sort of a "fitter's code", that had been applied by the person who had built this engine:
Single B... :
... Double B... :
... and a rare Triple B:
Imagine my surprise when I recently discovered similar stamps on BSA M20 engines! I didn't have to look far to find single B and double B stamps:
If this is "the same code", it can't have been a fitter's code. If it was used on Enfields and on BSAs, it must have been a military (rebuild) code...? But in that case, we should find it on Norton, Matchless and Ariel engines as well! 
This is where I need your help chaps! If we want to find out what the meaning of this code could have been, we'll need more examples! Bs or any other similar letter stamps (I have found similar stamps with other letters on Enfields as well, but the Bs are found most often).
If you can find a similar stamp on your engine, could you please post it here, or send it to me in an email. 
Thanks for your help,
Cheers,
Jan
email (option): wd.register@gmail.com
I have such a stamp...but the letters are much smaller. It's a one piece stamp with 'BB' on it. I am pretty sure I have some M20 WD cases with the B stamped on (not with my stamp!)...I didn't know you were a secret collector of M20 engines Jan..
...Ian
email (option): ian@wright52.plus.com
I think you just stamped your country initials in after you've read the number....
email (option): snvosselman@hotmail.com
hi,there was this queer chap who went to the tattooists shop
and enquired ''how much to have a couple of wasps tattooed on my
bottom?''the tattooist asked ''why do you want wasps on your butt,the puff replied ''its for my boyfriend,he likes a sting in the tail''tattooist replies,
''cant do wasps,can only do bees,will that do?one on each cheek''.queer agrees and endures the agony.
that night he tells his friend,''ive got a surprise for you''
dropping his pants,and bending over,his friend shrieks
''who the f++k is BOB ''
cheers rick
email (option): richardholt@rocketmail.com
Chris you are right about the inspectors, but! They had their own individual number. Like here on my Triumph.
The stamp is a broad arrow with an M underneath then the inspectors number under that.
I think Jan can tell you their inside leg measurement from his research. Ron
email (option): ronpier@talk21.com
Maybe the bloke stamping the "B" then the "BB" then "BBB" had a bad case of the shakes
If these are rebuild stamps they weren't put on Norton's They never needed rebuilding..... (or never made it back to be rebuilt)
My 16H cases have a broad arrow stamp like Ron's
email (option): horror@blueyonder.co.uk
So the 'B' must stand for 'Busy' or 'Bloody Busy'...
Could the 'B' indicate a Base Workshop rebuild ? or inclusion on a 'B' vehicle inventory ?
Thanks for all your replies!
Unfortunately no B or BB on this engine, but interesting numbers nevertheless! The M74 acceptance marking was applied to all contract C/5109 Nortons, plus the early contract C/5612 bikes (until # 9000 approximately). Your engine has its contract number stamped on it, which is quite unusual for Nortons. Contract numbers can be found on most Enfields and Triumphs though (see also Ron's Triumph picture above: C/6128 ). The acceptance marking M68 on Ron's Triumph was used on the early WW2 Triumphs until the Coventry Blitz. This inspector's shoe size was 9, don't know about his inside leg measurement however...
Meriden Triumphs (post Blitz) didn't have an acceptance marking anymore...It looks as if the B and BB stamps were used on BSAs and Enfields only... In that case it will be a silly coincidence... I'll stay with my "fitter's code" for the Enfields... until somebody discovers similar markings on Matchless, Ariel, Triumph and Norton engines!
Jan
email (option): wd.register@gmail.com
I wonder if no-one told the man wielding the punches at BSA that the ohv contracts had all been cancelled and replaced by M20s...and he started to stamp 'B30' on them all
Thanks for that info Jan
email (option): horror@blueyonder.co.uk
"B" stamp on Matchless crankcase:
No "B" but still...
Any ideas on the "M" marking?
email (option): ferrarakias@hotmail.com
Hello Kostas,
As explained above, the M74 acceptance marking was applied to all contract C/5109 Nortons, plus the early contract C/5612 bikes (until # 9000 approximately). Late contract C/5612 engines have an M318 acceptance marking (approximately # 9000 onwards). This inspector also checked all the contract C/6127 motorcycles, plus the early contract C/6653 production. The highest M318 frame number in my list so far was # 19493, so your engine (# 19518) narrows the gap with the next inspector a bit more... The next one in my list is # 21860, with an acceptance marking M129 (could also be M179, unfortunately I have no photographic evidence of this number...).
Hope this helps!
Jan
email (option): wd.register@gmail.com
Cheers,
Lex
DETAILS, DETAILS !!!
email (option): viaconsu # planet dot nl
Hans, I fully expect you mean the B details, so here the are, only one B though, any ideas?? LV7 is a part number.
So clearly from a G3WO, crankcases came from Norway, and there's a faint stamped oval with "JLO" in it, and that was a German engine manufacturer, maybe they reconditioned some Matchless engines after he war?
This happened a lot in postwar Germany, both as repayments, and to get the economy going again.
Cheers,
Lex
email (option): welbike@welbike.net
Hi Alex, Here are some photos taken in the JLO factory..No Matchlesses unfortunately...Ian
email (option): ian@wright52.plus.com
So clearly from a G3WO, crankcases came from Norway, and there's a faint stamped oval with "JLO" in it, and that was a German engine manufacturer, maybe they reconditioned some Matchless engines after he war?
This happened a lot in postwar Germany, both as repayments, and to get the economy going again.
Cheers,
Lex
Hi Lex,
The B on this engine is part of the "B189 MS114" marking. This is a rebuild identification code. B189 is the number of the TT3 workshop, 114 means November 1944.
I have a picture here from a Norton engine with a similar code (B189 MS124, same workshop, December 1944) and also a JLO stamp!
Next picture is a Triumph with a similar code (B189 MS745, same workshop, July '45), without a JLO stamp...
... But this also looks like a Triumph engine, no B189 code, but a JLO stamp can be seen!
Makes me wonder if B189 could have been the JLO works...? The factory is in Altona, close to Hamburg. Hamburg was liberated by the allied forces in May 1945... So it's impossible to have JLO rebuilds in 1944...
The search goes on!Jan
email (option): wd.register@gmail.com
So clearly from a G3WO, crankcases came from Norway, and there's a faint stamped oval with "JLO" in it, and that was a German engine manufacturer, maybe they reconditioned some Matchless engines after he war?
This happened a lot in postwar Germany, both as repayments, and to get the economy going again.
Cheers,
Lex
LV7 was the army stores part category and MC was the army code for Matchless
email (option): davmax@ntlworld.com
Just noticed that both the Norton and the Triumph engine in my previous post have a number 3787 stamped next to the B189 code. I have pictures with more than 10 different examples of similar Bxxx MSyyy codes, only these two appear to have such a number though... No idea yet what it means...
Jan
email (option): wd.register@gmail.com
Aaaah! The Norton engine has a brass plate with the same number! It's the catalogue number! So that's no Triumph engine, but another Big 4!
Jan
email (option): wd.register@gmail.com
The middle engine does indeed look to be Norton but the frame isn't. Was that the 16H lump in a pre-war Sunbeam from Netley Marsh ?
What a mistaike to maike!
I should have known that 79 x 100 is a 16H, not a B4! 
Indeed, the other one is the Netley bitza... I got a bit confused!
Jan
email (option): wd.register@gmail.com
This one was heavily priced at Beaulieu - Another AS spare engine that's been through JLO
These are generally quite early war engines. Probably on their second rebuild by then. Perhaps rebuilt in the UK before being shipped to NW Europe and then wrecked again after a few years of being thrashed up and down the autobahns by the B.L.A.
Apparently JLO spent the war years making heavy sidecars..I guess for BMW and/or Zundapp....Ian
email (option): ian@wright52.plus.com
Ron Pier just sent me this Matchless picture (thanks Ron!
), from a sister bike. Same letter B stamp... 
Jan
email (option): wd.register@gmail.com
Just thought I'd add to this 'B' business with a pic from my M20. The engine number has been stamped out (why?) and looks close to my chassis number with the beginning and end numbers being the same. Also, any ideas on the 03492 number on the breather?
email (option): lee@twowheelstested.co.uk