There was no specific typeface.  If the prize was a gag, I'd try using humorous letters.  For all other prizes, I chose not to use anything but a gothic typeface (no serifs -- like a Roman typeface -- that reduced the size and readability).  With limited space on each card and often long words that could not be abbreviated, like AIR CONDITIONER -- I had to use a condensed face.  In order for the studio audience to see it, aside from on one of the monitors -- I never used a letter that was smaller than 3 inches high.  At first, I tried to be true to the medium by used drawings instead of words -- prizes like a set of tires, a TV set, a diamond ring, etc. This didn't work -- how do you draw a trip, wall to wall carpeting, a micro-wave oven, etc.  Also, these renderings took much too long, and unlike the old expression: "Pictures speak louder than words" -- the words were easier to read.   Now, you've acquired a  little more trivia.