I don't know about the rest of the country, but here in New England we have 5 seasons: Spring, Summer, Fall, Winter, and Hubcap.

Hubcap, a.k.a. Pothole, season falls between late winter and early spring when the ground begins to thaw and roads disintegrate into treacherous, sink-holed paths designed to crack axles, flatten tires, and, at the very least, dislodge a fair number of hubcaps/wheel covers. Good Samaritans often prop the orphan caps up against fences and phone poles in hopes that their proper owners will recognize and claim them before collectors get them.

For some time now, collectors of hubcaps have fallen into 3 categories:

First, there's the entrepreneur. For every car owner who loses a hubcap/wheel cover, there is a car owner looking for a replacement. For every classic vehicle being restored, there is an auto restorer searching for original equipment. Brand-new original (factory) caps/covers can be expensive or impossible to purchase through regular auto dealers (try going to your local GM dealer and ordering hubcaps for a '57 Chevy BelAir or '66 Mustang). However, there's a thriving secondary market in used caps/covers. Now, it is highly unlikely that anyone would find a vintage hubcap by the side of the road, but the entrepreneur will search garage sales, junk shops, and estate sales for the potentially valuable disks.

Second, there's the artist/artisan. While some individuals are creating and marketing clocks and windchimes made of hubcaps, others are utilizing the disks as "canvas" for paintings or material for sculptures.

Third, there's the collector. Some collectors, recognizing caps/covers as splendid examples of industrial design, appreciate them for their elegant simplicity alone and collect all those that appeal to them. Other collectors may specialize in a particular model (Cadillac, Firebird, Mustang, etc.) or maker (Ford, Volvo, BMW, etc.) or type (threaded, spinner, custom, etc.). Easy to display, some collections take up entire walls while others are "filed" like lids in a rack.

Like any other collectible, condition is of major concern. Though used caps are not expected to be without some scratches, dings, and wear, those that are rusted, dented, or otherwise badly damaged are generally of little or no value.

For more information on hubcaps as oddities, art, and collectibles:

To identify a maker and/or date, check out any one of the many online retail sites such as http://www.hubcaps.org/makes.html or http://www.hubcaps-wheelcovers.com. They're all easy to navigate and provide clear photos.

Both Collector Online http://www.collectoronline.com (Click on "clubs" tab) and Collecting Channel http://www.collectingchannel.com (Click on "Maloneys Online" tab) list this as the only known club devoted to the subject:

The Hubcap Collectors Club
Dennis Kuhn
P.O. Box 54
Buckley, MI 49620
616-269-3555

Hubcap arts and crafts:

Hubcap clocks
http://digbig.com/3wgd

Hubcap creatures by British artist Ptolemy Elrington
http://www.hubcapcreatures.com
http://www.findaproperty.com/cgi-bin/story.pl?storyid=4649

If ever in California, you might want to visit California Historical Landmark No. 939. Considered the largest collection of hubcaps in the States, over 5000 are on display. http://digbig.com/3wgf and http://sanfrancisco.about.com/library/weekly/aa101398.htm