Here you go Richard, with the article by John Davis
http://docs.google.com/Doc?id=dfg2hmx7_1742r4n6vcz
T1 Lifter courtesy of Ron Conover with 'PB' in a shield, 'T', and unknown mark covered by the bottom rib. The 'PB' mark has been found on Laminated, Decarbonized and Twist barrels; the earliest SN 0954 and the latest SN 4576.
