I opened the engine of my m20 and saw in the inner side of both crankcase shells a star of david and in it the letters pbm or p8m. any ideas?

I don't know this to be fact for certain, but there was (and still is) a large Jewish quarter in Birmingham where they manufactured mainly jewellery..A friend of mine that was involved in the trade in Birmingham (and who also worked at BSA for a while) told me that there were also many Jews working in the foundries and other trades and that Jewish patternmakers put these markings into the patterns as an 'identifier'...It sounds plausible and as yet I have never heard any other explanation...Ian

email (option): ian@wright52.plus.com

thank you Ian

it is a mystery to be solved but your explanation make sense

Another possible explanation: When I rebuild a bike I punch my initials and birthdate on the inside of major components. If it's stolen and then recovered I would not have much trouble identifying it for the police, even if it has been broken up for parts or the regular serial numbers have been ground off or eliminated. Thankfully it has not become useful - yet?

email (option): jonny.rudge@verizon.net

Hi John..The Star of David is cast into the components..in other words it was part of the original wooden pattern, not a later addition...Ian

email (option): ian@wright52.plus.com

Hi John, what if you then sell a bike? The new owner has this stamped on every part. Your date of birth might be mistaken for a rebuild date etc. I wouldn't be very pleased.

There are lots of other ways to mark a bike these days, with smart water DNA sprays that are registered to you but aren't visible etc. My mate has just done his bike with it.

http://www.motorbikenews.co.uk/free-anti-theft-bike-dna-kit/

email (option): horror@blueyonder.co.uk

It doesn't stop anyone stealing the bike and statistically you are unlikely ever to see any of the parts again anyway..My Sportster had those awful 'datatag' stickers and etchings on many of the painted parts..Work currently being done on the bike will eliminate most of those. Frankly if it was stolen I wouldn't be over excited if the Plods turned up on the doorstep with a belt guard and a few other bits ..When my mate lost his 'owned from new and fully restored' Norton Commando he eventually got back the bottom half of the engine and part of the sawn up frame...He was quite upset as as it confirmed his worst fears...Ian

email (option): ian@wright52.plus.com

If I sell a bike I simply tell the new owner the places where the code is stamped and provide him with photos. It does not have to be "his" code, since it's only for identification and, in any event, the state's registration records will show all prior owners, if the cops need to verify it. I know it does not stop anyone from stealing the bike and it's certainly not my only "security" measure (my best security measure is my wife, who is in law enforcement and packs a 9mm with an extra capacity magazine), but as long as I have it apart, it's just a couple of minutes of work.

email (option): jonny.rudge@verizon.net

Note to self...'Be nice to Johns' wife if I ever meet her'.. ...Ian

email (option): ian@wright52.plus.com

Ah... yes, in that case you do what ever you want John. Hello, and have a nice day Mrs Harris

email (option): horror@blueyonder.co.uk

I believe the foundry mark referred to is actually PBM, does anyone know the significance of these letters? Are these the initials of a BSA or Birmingham foundry?

All six point stars, are not stars of David.
http://en.wikipedia.org/wiki/Star_(polygon)#Six-pointed_stars

All high volume BSA crankcases from at least 1937 were gravity die cast.
and have the PBM within a 6 point star.

The pre war gravity die cast crankcases have stars which are much larger than those found in war and post war cases.

In post war gravity die cast gearboxes it looks more like a hexagon surrounding the PBM.

Likewise late 30's to early 40's gravity die cast gearboxes have the letters J.H.L. associated with their casting numbers, but no stars. Anyone know what these mean?

Early to mid 30's sand-cast gearboxes have BA, which may mean Birmingham Aluminium, AKA Birmal. Is this correct?

email (option): n.gentner@bigpond.com