Welcome to the ATB club! Bought mine in 1989, and six years ago had a (removeable) tandem insert made by Doug Pinkerton, and a Rohloff hub gear fitted. Three years ago had an ARCC electric assist added.
It's the most rugged Moulton spaceframe model and takes the largest section tyres, it's my main bike in solo form for off-road riding.
Alex Moulton himself told me only about 100 were made, before the jigs went to Pashley to make the APB, and subsequently the TSR.