I like the head - viewed from above, the angle of the inlet and exhaust ports look to give a nice swirl.
The "sideways" nature of things does seem weird, particularly for a vertical single cylinder. But there was precedent in the sporting ohv Douglas twins, beginning with the Sports model in 1920, running through the Dirt Track and into the 1930s. Like the Matchless, all very sideways! Even earlier was the racing Matchless ohv V twins in the 1914 (?) TT, which used an unusual MAG (Motosacoche) twin with sideways heads. I wonder if the Matchless designers had one of these engines in mind when they began work on the LR in the early 1920s.
The missing bits - particularly all the top end of the valve gear - is certainly a problem, but it's the sort of thing that lurks in sheds as a curiosity, interesting but useless!
Leon