According to a recent email exchange with Virginia Scott of Beggar's Opera: "The tron I used on Waters of Change (Mk2) was bought by PFM back in 1971. I did contact them a few years ago to find out if they still had it...sadly it was disposed of." No idea of an operational definition of "disposed of" (trashed? sold? converted to coffee/end tables?)
Frank Samagaio San Diego CA ower, Mellotron MkII #13 (Pindertron) / M400 #908 author, The Mellotron Book