When my Parents ordered their new MF FE 35 X in 1963 from Coventry England the same wrench was in the tool box and is still there today:
Operators manual indicated wrench could be used to check Diesel Tank fuel level:
The marking on the wrench is it "CM" as in Centimetre's" ?
I'm wintering away from our summer home so am not able to verify the marking on the wrench.
Bob..Owner operator TEA-20 * MF FE 35 X as well as other colored Tractors: