The only Halibrands I can think of had smaller/shorter holes with a slight ridge around the slots.Many slot wheels had more squared corners than the Americans,like the Jeep wheels.Many had the air valve in the rim and not in the slot like the Americans.These have the step in the rim and center like Americans.The 8-lugs that I`m most familiar with had differences from the 15" wheels due to heavier application and larger diameter.The step in the rim is more pronounces and the slots are closer to the rim.Here are some Americans in 8-lug:

Here are some that are not Americans:

Halibrand

These were called "dish mags" before we started calling them "slots".The name "mag" was a reference to all early racing wheels made of magneseum,but mostly the 5 spoke design was considered a mag.The others used another word to identify them,like "dish".