Roger II - Rare Follis 1139, Messina (St. Nicholas, Spahr 76 / MIR 24) - Evaluation

[Arminio]

Hello everyone, I would like to share with you this rare follis of Roger II, minted in Messina in 1139, showing the bust of St. Nicholas on the obverse and the 4-line Greek inscription on the reverse (Spahr 76 / MIR 24, rated RR).
The coin comes from an old family collection. I am looking for opinions from experts of Norman coinage regarding its current market value in Germany/Europe and its grade, as I might consider parting with it if a serious collector is interested. Thank you in
advance!