Clyde's management duo bring their team to Govan this afternoon for an Irn-Bru Third Division encounter and if Duffy is the straight man of the partnership, McCoist shares a certain synergy with Charnley, the former Partick Thistle midfielder. Perhaps this is because, when he got into management under Walter Smith at Scotland, then Rangers, he was perceived as the jovial assistant whose job description it was to put a smile on his players' faces.
"They are a perfect double act – two contradictory characters," said McCoist. "Duff's teams are always well organised and well drilled. His wing-man is something else. I love Charnley. His is one of the old-school Scottish football entertainers. He played the game off the cuff. He is a throwback, a smashing lad and is very friendly with Kenny McDowall [Rangers assistant manager]."
Charnley, who played once for his beloved Celtic in a testimonial match against Manchester United, and recently served the club in a part-time kit man's role, made an impact after the club's previous meeting, a 2-0 victory for Rangers at Broadwood in October.
"There are not too many tales I could see in print about Charnley but one I can tell you is about the end of the game we played at Clyde," McCoist said. "He came up, shook my hand and grabbed me. He kept an aggressive face as he whispered in my ear: 'I want everyone to think I'm saying what Lennon said to you'. I said 'Great, Chic, but the fact I'm killing myself laughing would indicate you are maybe not being as nasty as you'd like to think'. There is never a dull moment when he is around. He will give the boys in the media a line and puts the smile on the faces of a lot of people."
That victory in Cumbernauld was something of a staging post in the Ibrox club's season, their first away win, coming immediately after losing at Stirling County and an impoverished performance in victory away to a 10-man Forres Mechanics team.
Prior to Saturday's trip to Elgin City, Rangers had quietly won seven games on the trot. "There has been a far greater level of consistency and results," McCoist said. "Winning at Clyde was important. Our away form and results hadn't been great, so that victory was greater than the three points in terms of confidence. We have been able to go away and keep picking up points, and our home form has been very satisfactory."
For all the bonhomie, today will be a serious business. Clyde are in mid-table but, although Rangers have some breathing space at the top of the league, smaller sides still regard visits to Glasgow as a showpiece.
"It will be tough for us," said McCoist. "Last midweek, you could see the Annan boys gained an extra 10% or 15% in terms of their application. It's a natural thing for players coming to Ibrox and playing in front of 40-odd thousand to raise their game. It's probably been one of Jim and Chic's hardest jobs to keep them focused on the games just before."
Duffy is hoping his players can repeat their level of competitiveness from the sides' meeting in Cumbernauld. It is Clyde's first league visit to Rangers since October 1974.
"We lost the game with Rangers at our place but the boys left with their heads high as they gave a good account of themselves," Duffy said. "All I can ask my team is to give another performance they can look back on with pride."
"We are a young side and playing in front of a massive crowd will be a great experience but I don't want the players standing back and soaking up the experience. I want them to show people that they are good footballers who would enjoy big games like this in the future. I know that they will put in a shift."