R1b1c9*, a, b - & - R1b1c10
There is, however, one exception - a grouping within the subclade S21+. What some have called "Frisian" with DYS390 = 23, if seen with DYS492 = 13, is in fact very likely to be S21+. However what I think many fail to realize is that about half of the S21+ group cannot be predicted in this manner. Curiously I have two Shetlanders with aboriginal (Norse) surnames who with 37 markers fit the S21 pattern but they test negative; however another who is Western Atlantic Modal Haplotype does test S21+. It is clearly bimodal, "Frisian" and "other". Being DYS492 = 13 or 14 is strongly suggestive of all varieties of S21+.
Subgroupings of R1b1c9 can however generally be predicted. R1b1c9a is seen when the testing DYS439 returns a null value. R1b1c9b has a fairly distinctive pattern of Y-STR scores.
All R1b1c9 of whatever stripe is to date found in the heaviest concentration in the Saxon - Frisian region (where it approaches 75% of the R1b1c in that location), and tapers off slightly into Scandinavia (where it is still the predominant R1b1c haplogroup), and falls somewhat precipitously as one travels to the west (except in England and Lowland Scotland where it can make up 50% of the R1b1c). The strong showing in Italy may reflect the footprint of Germanics such as the Lombards, or perhaps the remnants of those who over-wintered in that region while R1b1c* was basking in the Franco - Cantabrian area. To date a lack of data means that we don't know if eastern R1b1c, (e.g., Hungarian; Ashkenazi; Anatolian), is R1b1c*, R1b1c9, or R1b1c10.
It is now quite evident that there is no way to predict R1b1c10 from a haplotype, even at 67 markers. Ron Scott's database of extended haplotypes for SNP tested R1b is a good starting point. Most S28+ Y-STR markers are modal for R1b1c. I (being S28+) have the very unusual DYS444 = 14 (12 being a strong modal) but of the totality of the R1b1c10 with extended haplotypes, only one (ancestor from Kent County) shares this with me. There is no consistency whatsoever within the R1b1c10 haplogroup subclade - they "look" no different compared to R1b1c*, or R1b1c6 for that matter.
As to distribution of this haplogroup subclade there is a very definite "hotspot" in Switzerland, Alpine Germany, and Northern Italy. The majority of R1b1c whom EA has tested from this area are S28+, although we are looking at relatively small sample sizes. From this "epicentre" the haplogroup radiates out through the middle of France to the Bay of Biscay (France being a mixture of R1b1c*, 4, 6, 9 and 10 - at the moment I don't know which predominates). To the east it follows the path of the La Tene Celtic migration of the 4th Century BC, ending up in Southern Poland and the Balkans - and likely further east but there is as yet no data so nothing further can be said. There is an "isolated" enclave in Southern Scandinavia that has shown itself in the English Danelaw, those with aboriginal (place) surnames in Orkney (characteristic of Norse families), and coastal Eastern Scotland (only in those places known to have been settled by the Vikings).
Further research may confirm that R1b1c10 is one of the largest haplogroups found in Central Europe north of the Alps. Perhaps this holds true until interfacing with the large haplogroup R1b1c* groups of the west (plus their likely kindred R1b1c4, 5, and 7); R1b1c9 and I1a in the north; and the I1b and R1a1 populations of the Slavic - speaking world in the east. To date there has not been an exception (time will likely cure this) of S28+ being found outside the known areas of 4th Century La Tene Celtic migrations and settlement. Hence for the present we might tentatively term it the "La Tene Celt marker". Perhaps some will find this a tad presumptuous or simplistic - but nothing ventured, nothing gained. In this instance there does seem to be a noteworthy correspondence between the distribution patterns of archaeological assemblages of the Hallstatt and La Tene eras, and this particular genetic marker. Based on this observation I predict that ancient DNA testing of, for example, the La Tene cemeteries in Bohemia (home of the Boii tribe), but also the burial places of the Helvetii and related tribes of the Alpine regions, will predominantly test R1b1c10 (S28), as will the present day R1b1c populations of these domains - they being descendants of the "Ancient Celts".