Based on the most probable derivation of the Surname BARTOLD, I wanted to see where the various relatives are now. Unfortunately, I've only started on this part of my project, and I only have concrete numbers from Poland. I still need to find the proper references for France, Italy and Germany. The name is scattered around the USA and Canada also, obviously from Europe, and there is even one clan of Bartold's in Australia, having emigrated from the German (Prussian) ruled Mecklenberg region.
In the recent "Słownik Nazwisk Współcześnie w Polsce Używanych" from Kazimierz Rymut, published in Kraków 1992, we find the following listings:
The Biert- prefix no longer exists in Poland, and we can see that the Bert- prefix is quite rare. No other reasonable letter combinations exist. The two-letter abbreviations are breakdowns for the current Polish provinces (województwo) numbering 49.
This indicates that the Bartołd's are centered in ciechanowskie, and the Bartold's in stołeczne warszawskie. The Berthold's are further west, centered in leszczynskie, and probably are not decended from the Bartold line, or the name became Germanized while that region was under Prussian rule.
For comparison, I also include the non-Bartold names (i.e. those not ending in a hard letter) that occur, mainly in the north:
Being curious, I decided to run the various versions of the Bartold surname through a SOUNDEX program, and the results were very good, although I'm not sure how the program actually dealt with the polish Ł, which SHOULD sound like an english W. Anyway, the name was written (in part influenced by the German or Russian rule) in loads of forms, which could be expressed as a combinatorial expression: [BAR|BER] [T|TH] [O|Ó|U] [L|Ł] [D|T|DT] which results in 72 different forms. Luckily not all of them occur and fortunately all have soundex codes of B634 or B633. The main variants in modern Poland are BARTOŁD - B633, BARTOLD - B634 and BERTHOLD - B634.