Hymnals in churches are no longer in their prime. The day of a worship leader announcing a number, pausing for everyone to turn the pages, and then singing together has begun to fade. All the responsibility rests on one person who must make sure the next slide is projected on the screen at the exact right moment. I'm not sure how familiar my son will be with a hymnal as he grows up but I certainly was familiar with the one we used in our congregation.
The most popular hymnal used in my tradition was Songs of the Church. It contained a list of 10 commandments on how to be treated. Things like "Thou shall not use me to spank children" and "Thou shall return me to my proper place when not in use".
But what people will remember most is the hymn number 728b. There was no 728a or 729, just 728b and people wondered why. Sometimes it was referred to as the national anthem of the churches of Christ. The title was "Our God, He is Alive" by A.W. Dicus. It was a peppy song where every church had their favorite way of singing the chorus; fast or slow. Nonetheless, it was a song that brought unity to people in the CofC tradition.
Anyway, my intramural team in college all chose weird numbers for our jersey's like 3.14, 12, and 728b. That number has played a significant role in the life of many. In fact 728b.com is "coming soon", although I don't know who is bringing it or what it will be. I can only guess they too were impacted by the song. There's also a cool band that has embraced the number - they're called 728b. You can also buy some church of Christ items in the 728b store at Cafe Press.
So if you want to know how old school church of Christ a person is, ask them if they know about 728b.