History according to Auto World:
1967: New Riggen JAD RTR car, only Harrison Formula listed, Weldun crown and pinion - $12.95
1967 Fall-Winter: Watson Ford, BRM H-16 and Chappie XL, Cox pickup, self-lubricating crown, 12.95
1968: Watson-Ford, BRM H-16, Chappie XL, Riggen Special, Ferrari Custom Coupe (and a P4 Spyder pictured, not identified!). Gears and quick-change brushes by Cox (2.9:1), still 12.95 except for Special (9.00) and Ferrari (11.95)
1968-1/2: Watson-Ford, BRM H-16, Brimhall Lola T70, Chappie XL, Riggen Special, Ferrari Custom Coupe, Ferrari P4, Nylon GS-51 gears by Riggen, all 11.95 except the Special (9;00).
and that bring us back to 1969... Same as 68-1/2, except the Dune Buggy is new, and all cars now priced at $9.00!
By 1970, one page of Riggen cars, all with the flat pan chassis...
It's a happy ending: everybody's right!
Don