I finally got a chance to take a video of the 172 RG Gear today, the later 210's used this Tubular gear as opposed to the Flat Spring steel gear in the earlierones..

Here are some detail pics and a video link,

http://www.rcuvideos.com/item/MTSQH85G4SNV95V8

Sorry it took so long but we just brought it back in for it's 100 hour

The tubular gear started in 1976 If I believe, and it originally had gear doors.
about 1980 the doors were eliminated since they were sequenced hydraulically and could get out of sequence with the expected expensive results!!!!!

so a kit was developed to retrofil the non gear door setup onto older Tubular gear 210's.

Also the 337's definitely did not have tubular gear in their entire life span.