Just checked, with source ( who is a little shy, and would rather remain unidentified ) but did play in the 1983 Wembley Showpiece ( that narrows it down a little ) and he assures me that the coin toss story is in fact true, and was told to him verbally by either Keith himself or Laurie Gant he cannot quite remember which.
Unfortunately, this cannot be verified as both these 2 great servants of Featherstone Rovers are coaching elsewhere I imagine, willing the class of 2010 to stay focused and continue their efforts !