Reason I asked is that Magnesium as a wheel material hasn't been used since the Halibrand wheels of the early 60's, except for Indy Cars, F1, GT Prototype and Trans Am series cars. It is expensive, a pain to machine, tarnishes in a matter of hours, and brittle compared to aluminum. Just because the public called most aftermarket wheels "mags" doesn't mean that they were actually made of the stuff, it is just the lingo we used.
Your wheel looks like a common aluminum wheel sold by ET Enterprises in the 70's, my uncle has a set on his all original 30,000 mile '73 Monte Carlo, the only difference is that the background around the spokes is painted black and the flats of the spokes and rim edge are polished. He bought them new in the mid 70's and they have never seen snow and rarely rain. Now that you said they have been blasted it makes sense that the finish is different, and it even looks like your center caps say E/T on them in the pics.
These wheels didn't come in very many sizes or offsets/backspacing, and 8.5" deep dish style will be the widest you will probably find, and won't fit under the fenders of your TA because of this dish(remember airshocks in the 70's). Don't think I have ever seen another full set of these at a swap meet, you won't find them new as they haven't been made in 25+ years.
The variety of wheels today has spoiled us as far as sizes and offsets, it wasn't that way back in the day, there were only a few companies and styles and nothing wide over 8" fit under the fenders without flaring them or narrowing the axle.
Cole
