Eric

The American racing Libre (NOT Libra) wheel from the mid '60s was the smaller brother to the 5 spoke 200s wheel. The wheel was intended for imports in the 13" and 14" sizes. Commonly 13x5.5" and 14x5.5" 13x7 and 14x7 were also available. Magnesium race-only versions may have been available as well, but I'm not sure. They were popular on the Datsun roadsters, 240Z, 510, early Toyota Celicas, Sunbeam Tigers, MGBs, Cortinas, and the like. (FWIW, rumor has it that Pete Brock himself styled the American Racing Lemans wheels)
The Libre wheel has been copied by many over the years, but I can't tell you more than that. I believe Carroll Shelby Wheels may have copied the design. The wheels were also re-issued in the 13" size for the SCCA's Ford-powered Spec Racer (SRF), though these wheels had "SCCA" cast into them.
The differences in casting of the reinforcing ribs behind the spokes, mounting surface thickness, and rim edge profile, vary between the various copies. All the ARE wheel have the identifying marks you mentioned.
These sand cast wheels were not very well quality controlled in their day, and many recommend that the genuine vintage wheels be used today for show only, as there have been reports of failures of Libres at speed.

Kurt Hafer
Datsun 510 Wheel FAQ

Eric

As you know, there were several types of 14" Libre style wheels built. Of course, the most famous is the American Racing version, and they are always marked with their name on them. Carroll Shelby also made 14" Libre wheels, and they are marked on the back as well. I have also seen several versions of 14" Libre wheels that were unmarked on the back, and I have no idea who made them. Then there were the magnesium versions! You can usually tell them apart as the spokes are a different design and come to a partial point where the spoke meets the rim. Here is one photo online of them:  Below is another part of a photo which shows those wheels better.

Michael Spreadbury
Spriso Motorsports