The pre-war model 30 trainer is a straightforward single-shot, tap-loading, underlever design (many other German trainers of the time were magazine-fed ball-shooters, completely different designs in spite of a similar exterior appearance). In detail it is similar to the post-war model 50, but rather smaller, kinda like an underlever version of the model 27 barrel-cocker.
One of these guns in good condition should be a hard and accurate shooter, well out of the bb-gun class.
Gentleman says it is complete in 80% condition, I'll know later today.
He's not too far from me so I'll take a look. He was parting out a number of firearms and I asked about airguns. The Diana 30M is most likely a resale piece for me to pass onto someone who collects.