Hi Kate, I seem to have found your question a bit late.
A footballer used to get a cap for EVERY game he played in. This is not the case these days, for instance if you play in a tournament, say World Cup last summer you would be awarded one cap covering all the games you played in and these games would be detailed on that ONE cap.
Ian McMillan played 6 times for the Scottish first team and would have received 6 individual caps.
He played against England, USA (scored twice) and Denmark in 1952. In 1955 he played against England and in 1956 he played against England again. The total of 5 games was when he played for Airdrie.
He joined Rangers in October 1958 and played his last game for Scotland on 14 May 1961 against Czechoslovakia in Bratislava - Scotland losing 4-0. He played this game whilst a RANGERS player (which is the information you were after).
He also played once in a Scottish 'B' international and made two appearances for the Scottish League. I have been unable to trace the exact dates for these games but would assume that these were made before making his full debut for the Scottish first team. In other words these games were PROBABLY played during his Airdrie days.
As a matter of interest he would have received caps also for these three games. The issuing of caps for games given to Scottish appearances are somewhat different to those awarded to English players at this time - he may have been issued a commemorative medal instead and in most cases would have been allowed to keep his match shirt.
Ian McMillan had a most distinguished career at Rangers and on top of this was only a part time player with them.
I hope this helps - regards, Mark