I have just started finding out about bread stamps. Does anyone out there know about this way of marking loaves?
The most interesting website I have found in this relates to bread being baked for orthodox Christian communities: http://www.prosphora.org/index.html 
Complete with a page about the physics of how the stamps work: http://www.prosphora.org/page37.html 
I'm interested because marking loaves with some sort of makers mark would fit nicely with my current research/art project involving baking bread and swapping it for objects of equivalent value.
Attached are photos of my last event where I went into a gallery for three days and produced 500kg of white sourdough. Was it any good you ask? well I think it was the best sourdough baked in a gallery that I've ever seen. I'm a artist not a baker so some of the batches were a bit inconsistent. You can see the photo of the collection of stuff I swapped over the three days.
I'll also answer earlier comments about this project being wasteful or bad art that are in another thread.
Of the approximately 500 loaves baked, 250 were swapped for objects. 100 were given to people and organisations that helped out. 50 went to a music event to feed the masses and 20 were sent to the worm farm (something went very wrong with that batch) The rest probably got eaten on site or somehow found their way to happy mouths.
Quality in art is always hard to judge but any work that sends audiences away smiling and has parents bringing kids along to try and explain value, barter, baking and art I think can't be all bad.
The plan is to hold three more of these events in the next twelve months in different places to see what the variation in what is offered. It's all part of the research for my PhD in the area of participatory art.
Sorry I'm not writing more. I dropped the oven on my fingers and fractured two when moving it out of the gallery back to my shed.
SORRY I'M HAVING TROUBLE DRIVING THE PHOTO INSERTING FUNCTION. APOLOGIES FOR THE PHOTOS BEING ALL OVER THE PLACE.