most of these wares were widely distributed and produced on an industrial scale (the largest kilns could fire up to 40,000 pieces at a time ), and undoubtedly using a high degree of specialisation within the workshops. the names of many potters and factory-owners are known from the potters' marks frequently applied to fine wares, and can be highly informative. cnaius ateius was an especially prominent producer at arezzo, but wares with his stamps can be shown by modern analysis of their clay to have been produced in pisa in tuscany, and at branch factories at both lyon and la graufesenque in modern france. however, the interpretation of name-stamps can be more complex than it appears at first sight. bold name-stamps visible in decorated areas advertise the name of the factory, but the names of individual artisans working within the pottery, the bowl-makers, appear on plain vessels, while the moulds for decorated bowls were also sometimes signed freehand by the mould-makers, and their signatures also sometimes appear on finished vessels. theoretically, a decorated vessel might bear the mould-maker's name, that of the bowl-maker or finisher (for example, on the rim), and the 'brand-name' of the factory in the decoration. the use of slave labour in the italian workshops is unproven, though some names are certainly of " (freedmen, that is, freed former slaves). the site of la graufesenque in south gaul, near millau, has been extensively studied and excavated. its products had an immensely wide distribution in the later 1st century ad, and sherds have been found from india to the sudan and scotland.