Allow me to be the latest to join (at least - I get the digest, so I might be a little behind) Denis Gojak and Michael Berry in noting that Glasgow was a major centre of clay pipe manufacture in the 19th century.  Glaswegian clay pipes are found almost everywhere that there was a British export market, from New Zealand to New Brunswick.  They're common on 19th-century sites internationally.Others have already provided dates for the various Glaswegian firms, and have supplied several excellent references, but for an additional quick and easy to find (I hope!) citable reference that should be readily available to colleagues based in North America, try:Bradley, Charles S.2000     'Smoking Pipes for the Archaeologist'. In Karlis Karklins (ed.) _Studies in Material Culture Research_.  Society for Historical Archaeology pp.104-133.The full Karklins reader can also be purchased on the SHA's web page for USD15 at:http://www.sha.org/commerce/publicationsCatalog.cfmAlasdair Brooks