I reinstalled my newish Takegawa replacement clutch, refit cover + stand + levers, added oil and went for my very first vintage-bike meet up. As expected, the ST70 was the smallest bike attending. As hoped for, people were taking pictures and asking questions.
Back in 1973, a total of 3000 ST50's were sold as 20 mph mopeds in Denmark. To my knowledge, no more than 5 of the 3000 have been converted into motorcycles. And only one has been registered on period-specific plates.
This one.
Edit: I've taken racerx's good advice and replaced the OE countersunk oil-spinner bolts with A2 steel allen-key replacements. A pack of 10 (ebay item 111309615915, length 10mm) cost me approximately 2 USD. It's now so much easier to clean the oil spinner.