Last time I checked, real Cobra R's had some sort of marking by the valve stem. Yours don't look like they do. However, real ones did have a serial number stamped on the back so I'm kind of confused. Maybe the R58's had the outside marking and the R50's like yours had the inside marking?
I had 6 real R58's yours indeed appear to be R50's. The early R58's are more desirable do to them being lighter and they actually say "made in Japan" on the spoke. As far as what there worth? I paid $50 a wheel of craigslist.