“I hope we have have brought you happy memories,” Elaine said.

“Indeed, you have.  Time for my instruments to run my tests,” Tzoltzin nodded appreciatively.  “You are attesting that this is the root drive on the alpha drive patent tree?”

“We so attest.  We hope it is the true first drive,” Elaine answered, “and requested an inspection to confirm that it matches the unpatentable root design. We recognize the possibility that we have misinterpreted some aspect of the specifications, however clear they seem to be.”

“Our treaty allows rebuilds to come into compliance with the specifications. My instruments will take a while to do check.  Perhaps for the nonce we should sit, let them do their work, and drink more of your excellent tea.”  Tzoltzin waddled back to the tea table.

“I’ve made a fresh pot,” Mabel Brixton said.

“Excellent.  This will take a while,” Tzoltzin said.  “The root drive is extremely large and complex, though in a sense it is simplicity itself.  Each part has only one function.  I do have a  note to myself, to remind you that there is a shape patent on changing the drive field shape.”

“You are referring  the surviving First Empire patent on these?” Elaine asked innocently.

“Precisely,” Tzoltzin agreed.  “The First Empire let the inventors gain a patent that covers ‘any design change that leads to the same effect’, in particular any design change that changes the volume englobed by the drive field from the useless pancake to the sensible cigar. And, indeed, there is such a shape patent, in the hands of – it’s in the files.”

“That’s all right,” Elaine said.  “Our interest is in validating that we actually built the root design.”

“A highly interesting choice,” Tzoltzin said.  “Perhaps someday I will learn why you find this choice interesting.”

“Indeed,” Elaine said. 

“On the other hand,” Tzoltzin said, “I am reminded of visiting here once and again, watching you build your new heavily over-built test bed, observed your delight that it flew using beta drives – a completely unsurprising event, since the quality of your precision construction is perfectly sound – and being entirely baffled that you then incorporated it into a freighter hauler of unconventional oblate discoidal form, a hauler soon to fly.”