OK here you go...the original were made of magnesium alloy and smooth paddle and a later version were made of aluminum alloy....
I have 3 Riviera Wheels marked on back:
4.5x15 / Patent # D216507 / PLM / Meets SEMA SPECS 5-1
4x130 Bolt Pattern...Backspace 3 ⅞ “
Riviera 15" x 5.5" alloy wheels (aka "Formula Vee" or "G.T. Mag Type")
This type of wheel was originally a VW Dealer installed option package from the Formula Vee accessory range. They were manufactured by Portland's Whitney Industries, Inc. and designed by co-owner Michael Gibbons. The actual casting was done by Pacific Light Metals Foundry from A356-T6 tempered alloy, a special aluminum-magnesium-beryllium-titanium alloy. "Lightweight and very strong."
They were originally made for the Riviera Motors owned Volkswagen Dealerships, a Beaverton, Oregon based regional distributor. Orig. part #X601 011
4 x 130 mm bolt pattern fits 1968-79 Bug, 1971-79 Super Beetle, 1968-74 Ghia, 1966-73 Type 3, may also fit other years and models with the use of wheel adapters.
In the USA Formula Vee magnesium alloy wheels were manufactured by Whitney Industries, Inc., designed by partner/owner Michael Gibbons and made for the Riviera Motors of Oregon owned Volkswagen Dealerships in 1968. Later made available to all US VW Dealers as part of the Formula Vee range – listed as the ‘GT Mag Type’. The casting was done by Pacific Light Metals Foundry from A356-T6 tempered alloy, a special aluminum-magnesium-beryllium-titanium alloy – lightweight and very strong. From 1972 Superior Industries ‘Turtlebacks’ were available.
They appeared in the 1970 VW ACCESSORIES BROCHURE and were called "MAG OR GT MAG TYPE" and later reproduced by Pacific-Italia as "RIVIERA".
Click to view attachment