There are two clusters of men with surname Matheis in J2b-L283.
One consists of about a dozen STR tested men with different paper trails to Matheis and variant surname ancestors mostly from southern Germany. One of these men did Big Y and recently got his own branch added to the YFull YTree below J2b-Z34474. That particular line has an ancient sample found in Iron Age Etruria.
Another J2b-L283 Matheis descendant has been confirmed to be J2b-Z1043 so he is not a genealogical time relative to the other Matheis cluster. They are distant cousins sharing a MRCA who lived 4500 years ago.
This second man has no Matheis surname STR matches but does have other German surname matches and we are waiting on their responses.
I found that he shares a few rare STR alleles in common with a man tracing descent to a Halabi from Aleppo, Syria. This man is so far J2b-Z1043*, meaning he's not positive for any line yet discovered below J2b-Z1043.
There are a handful of other men, some proven to be unrelated to our Syrian, sharing one of their rare alleles, DYS413 = 22-23. So this rare allele being shared on its own is not a strong indicator of having a more recent common ancestor.
The other rare allele DYS556 = 10 is much rarer. I see only one other man with this allele, myself. I'm proven not closely related Halabi who is J2b-Z1043* as I'm downstream J2b-Z1043>Z8427>Z8424>PH1080. I'm more closely related to a cluster of men from England who did not inherit this rare allele, so I probably inherited it from an ancestor who lived only in the last 1700 years.
The good news is that this Matheis has ordered Big Y and we will soon learn by his SNPs if the rare STR signature he shares with Halabi is indicative of a new, possibly Iron Age branching point of J2b-Z1043.
We hope to identify Iron Age branching points where men have geographically consistent male line origins in order get a better idea of the deeper origins of J2b-Z1043.
There is a lot of space between Germany and Syria but if these men end up being related, we would then know what STR signature to look for to find their other relatives, some of whose paper trails may lead back closer to the geographic origin of their MRCA.