AFAIK, the contra-prop variants of the Griffon, apart from the 57/58 on the Shackleton, were the 8x and 9x series, used mainly on the Seafire 46 & 47, so I would Google for photos of those marks.
If you have a Griffin 65 with contra-props then it's definitely non-standard - the Spitfire XIV, XVIII and XIX that used the 65 were definitely single-prop.