Gordian III Romae Aeterne coin with error

Your opinion to value? 

This coin with reverse ROMAE AETERNE instead AETERNAE is not common. How many pieces could be known?  I have to catalog number only this: “RIC IV-3 70 note”.  Do you know the number in other catalogs? 

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Hello there is one into the book of Briac Michaux “le monnayage impérial de Gordien III  238 - 244 ap J C” (dossier du cercle d'étude numismatique n°5)

page 79 collection L M with same pair of dies, R5 

Thank you Eric.