"Gear down" became standard as a final call, due to the variety of indications in military aircraft. For example, bona jets had 4 greens, F-4s had 3 wheel icons. But even after 'gear down' had been in for years, some Hercules co-piglets were still calling "Finals, gear checked".... One exasperated Local Controller at Brize eventually became so fed up with non-standard JATE-cowboy R/T that he advised that landing clearance would not be given until the C-130 crew confirmed that their landing gear was indeed DOWN!
"Roger, clear Land, Dunlops danglin'", is probably a serious no-go then?
CG