The first car delivered by Rohr was A car 101, a prototype car used to identify and resolve various bugs with the new cars' construction and simulated operation.
The 101 rolled out of Chula Vista (on a trailer) and was delivered to Hayward Shops on 8/27/1970. Unique among the fleet, the cab of 101 was painted grey/silver - other protoype cars had different colors of cabs. For about a month, A car 101 was the only Rohr car delivered, so there are a few pics of this single car rolling down the A line (attached).
Like most of the protoype cars, the 101 was returned to Rohr (c. 6/1972) and scrapped. From what I recall reading, Rohr decided it was not worth the effort to rebuild these A cars, and replaced them with new A cars (A car 101 II -> B car 821 -> B2 car 1821 in this case).
"The Two Bagger" is meant to be a place to store more "blog" style posts on various cars, pictures, and random tidbits. At BART, a "two bagger" is a rather informal name for a two car train. Two car trains rolled in revenue service back in 1972.