Interesting search. Here's the only reference I've found so far. It's a list of prohibited weapons in Hong Kong:
Travellers are liable to prosecution if they bring into/out of Hong Kong any "weapon" which includes Chinese-style throwing dart, gravity knife, gravity-operated steel baton, knuckleduster, Chinese-style fighting iron, spring-loaded steel baton, any knife the blade of which is exposed by a spring or other mechanical/electric device, and any bladed/pointed weapon.
Source
I wonder if this is a term a bureaucrat came up with? If so, I wonder if it has a proper name in the martial arts community? At a guess, Clavell came up with the name after reading the customs form on his way to Hong Kong for research, or something similar.
Search continues for a picture.
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