If a hybridizer is consistent in terms of how they label crosses, you can actually glean quite a bit of information about an iris from just the seedling number.
Just a random example, Keith Keppels iris 'Another Suggestion' has a seedling number of 06-156G (
Tall Bearded Iris (Iris 'Another Suggestion') ). That tells you that it came from a cross made in 2006, it was cross number 156 of that year, 'Another Suggestion' was the 7th seedling (G being the seventh letter of the alphabet) to get a number from that cross, and 'Another Suggestion' is a sibling to 'Friendly Advice' (its seedling number is 06-156Q).
I believe Paul Black uses a letter to designate the year of his crosses. All his seedlings that have a seedling number starting with, say, "R" were hybridized in the same year. All of the seedlings with numbers that start with "S" would be from the following year's crosses, etc.
I largely imitated Keith's numbering system except I separate the crosses by class. So, 'Livy' has a seedling number of 13T-11b, which means it came from a cross made in 2013, it was a tall bearded cross, it was the 11th successful TB cross that year, and it was the "b" seedling (that particular cross got as far as "p").
Similarly, this standard dwarf bearded seedling is numbered 13D-01c for a cross that was done in 2013, was the 1st successful SDB cross that year, and was the "c" seedling.
I don't know how others do it, but I don't give a cross a number unless it actually sets a pod. I do keep track of the unsuccessful crosses, but not giving them a number allows me to easily sort them from the successful crosses in my spreadsheet.
If I had it to do over, I might either copy Keith's numbering system exactly or use Paul's, simply because typing 15T-01a, 15T-01b, etc., etc., on my map of the seedling beds is really tedious. For me at least, more tedious means more prone to errors. Simpler is better as long as it's a logical system and results in a unique number for each seedling.
