The logo on the carbonized Pompeiian bread

[Dan Diffendale]

I'm at a loss for anything further, but maybe this will help you:

An actual bronze stamp was found at Pompeii that says
"L. Auruncule(i) Secundioni(s)",
while some carbonized loaves found read
[C]eleris Q. Grani | Veri Ser(v)
"(work of) Celer, slave of Quintus Granius Verus."

Here's a much later stamp:
[url:l0h75v3r]http://www.vcoins.com/ancientcoinart/store/viewItem.asp?idProduct=261&large=0[/url]

Ok, here's "Bread Stamp Physics"
http://www.prosphora.org/page37.html

http://www.ancient-art.com/images/a511.jpg

Hey, here's a legionary bread stamp!
http://www.gtj.org.uk/blowup.php?lang=en&id=25420&t=1