here's a place to start your search, I'd guess mid 60s or newer? http://www.hubcaps.org/chevrolet.html
Information helpful to identify hubcaps(the small ones) and wheelcovers(what you have): Wheel size they fit? 13,14,15, etc. Look inside them, sometimes they'll still have a part number inked on them or a paper sticker with number. A plain jane wheelcover like that one would most likely have been the standard equipement on a secondary series of car, like BelAir or Biscayne instead of Impala or Caprice. Many wheelcovers and hubcaps are still available through dealerships parts departments and some are illustrated in their catalogs/computers.
1965 chevy II. found a picture of them in cars of the sizzling '60s book, but i don't have a scanner. looks like them on page236 if anyone has that book.
early chevy II ....they are a small cap compared to full size ...might fit a 60's mopar steel wheel..... brandon