Again, I'm sure you already know this...

Here is something I genuinely did not know. Numbers, for all intents and purposes have an upper and a lower case, although they do not go by that naming convention. "Upper case" numbers are called titling figures, and "lower case" numbers are called text figures. Anytime one has numbers in a string of all caps the numbers need to be set in titling figures. Anytime numbers are inside normal text one needs to use text figures. This is how it always used to be until the modernists tried to simplify typography (they failed) which is why using text figures is also called "old style" numbers. The practice waned in the 1800's as Advertising proliferated and typography became cluttered, but it returned for a while until the modernists tried to kill it. It came back again until the 60's photo-reproduction killed it again, and then the 80's started to bring it back. A lot of classic faces like Futura didn't even have text figures until the mid eighties when the practice came back. The practice requires hidden keys now, but it's worth it. Write a line and try it both ways. Which do you like better.