Of the three left, one is groucho territory and I don't expect anyone else to get it but the two 60s ones are relatively well know players.
One of them broke into the team briefly in the 1962-63 title winning season then left a year or so later and won just about every trophy you could win at man city. He's someone I'm surprised hasn't been guessed yet.
...I'm thinking George Heslop but I thought he might be a bit later. I remember going to City in 66, we eventually beat them but I think he was City's centre back so I suppose he could've palyed for us a bit earlier?