The 210 went from flat steel legs to tubular in around 1978 (the 1979 C210N certaily had tubular gear legs), and lost the maingear doors around the same time. The 182RG always had tubular gear (from memory) as did the 172RG. I'm not too sure about the 177RG but I suspect it always had tubular gear. The 182RG and 172RG never had maingear doors, but I don't know about the 177RG. That's one of the few Cessna singles I've not flown.