Model Airplane News, Oct, 1948, Page 28 #6, Photo of original Joker. Comment about #6, page 58,
"No. 6, sent in by Capt H. M. Bourgeois, was designed and built by O. K. Foster (address). The Joker is powered by an Anderson Spitfire and does 90 mph, weighs 2 lb. 14 oz. Note 'Hap' the hot pilot, in the cockpit with complete radio gear and instrument panel. Plane has an hand rubbed finish of feather grey, trimmed in trumpet gold with carmen red pin stripe. The super finish and details were necessary to win the 85 points given for finish and workmanship in a stunt contest held on the West Coast. The Joker is a very stable flyer and capable of any maneuver possible with a controliner. Incidentally, the plane is six months old and has over 500 flights (with nary a crackup) to its credit. Photo was take by Norman T. Van Pelt who is a controline modeler and master photographer."
Given that the October issue was published in August, adding two months lead time between the writing of the letter and the publication of the picture, plus the six months mentioned; it is very likely the airplane existed in some form during 1947. A later 1948 MAN has it listed, in an ad,as an available kit.