Letters to the NGS/CIG DIGEST indicate that others have worked out their own "modified Henry" systems. Some use alternating letters and numbers, others all letters. One reader -with relatively few records - assigns each person two digits and separates these with a dash.
The major drawback of these numbering systems is that they lack acceptance among professionals. And the many variations in themselves can cause confusion among readers going from publication to publication. But they do allow you to look at the number and trace the individual back through the generations.
For computer purposes, the "modern" modified Henry System has distinct advantages over some of the other modifications, in that each generation takes one and only one number or character, thus saving computer space [compare 6A7B9 with 6(10)7(11)9]. Also, personal computers sort in "ASCII" code sequence, which means that 6A will immediately follow 69. Also, 691 would be sorted in between those two.
The modification that uses parenthesis, along with the d'Aboville system, because they use all numbers, do provide the easiest method of tracing back an individual's ancestory. Devine says one of the main advantages of the Henry or similar systems is that it allows for placing newly found children and their descendants without the wholesale renumbering necessary with the Register or Record systems. Renumbering is also somewhat of a problem for Henry-type systems. A reader noted: "If additional genealogical research uncovers another child, who should fit in between two other children with consecutive numbers, there is no way to make this happen, without renumbering the existing children."
This is a problem if you're trying to keep the children in chronological order and the newly found one is the oldest of a dozen. However, if you're keeping your records on a word processor, careful use of its search/replace feature makes the changes much easier. If you're using a nongenealogical database program, you can develop a process to automatically make such changes.
One NGS/CIG DIGEST reader pointed out that a numbering system which requires one character per generation means that in order to provide for 40 generations, data records must be set up to contain that many characters, even though most of them do not use all 40 characters. Again, for most of us, this is not a practical restriction - but it is one to keep in mind.
This same reader noted that hexidecimal numbers run out at 15 (hex F). "We all know of families with more than 15 children. Even if one extends the concept to include all of the alphabet one reaches a maximum of 35 (9 digits and 26 alphabetics). Checking the Guiness Book of Records shows that even 35 is insufficient." Again, something to keep in mind, but not a real restriction for most of us. A family beyond 20 - even 25 with several wives - is rare. One could even add another 26 child identifications by using upper case letters the first time around and lower case the second - computers distinguish between the two.