Kevin,

I think your hypothesis is good..I know my car is a "1" series, so that makes sense, but I have had others say that they have seen two digits stamped there..as in "16" so I'm not sure...I wondered about a second line or another line, but did Fisher produce all Chevelle bodies on the same line or were that multiple lines..I would think the later as well.. Also why not include this on ALL of the bodies if it denotes a series production of the line...For instance why would the plant only include the number on Baltimore cars, when other plants had mulitple series as well..1xxxxx, 2xxxxx, etc..??