A little Packard research on single and double Pilot ray lights others found for me:
Packard general letter G-110, June 26, 1929 describes the pilot ray lamp, at this date, it is illustrated only with a single lamp.
Packard Service letter Vol.4 no. 9, May 1, 1930. "New Accessory Items Announced "PA -1387 Dulpex Pilot Ray light - two lights mounted on same spindle housing and operating together. List price $65.00 attached".
Working on my 1929 640 Club sedan - wanting to explore period correct lighting options.