Thanks Geoffrey. That's a valuable site, one I hadn't yet come upon. And indeed it shows no use of any but local issues in Bosnia-Herzegovina.
Here now is the stamp that has prompted my query.

It's from the issue of 1913 (MiNr 117X). The place of cancel consists of two words. The first is apparently long, but only the final letter A is visible. The second word seems to be "VRELO." The L is unclear, but I haven't found another letter that would produce a better result. Nor have I been able to find any place in the Hungarian crown lands that included that name. There are, however, several places in Bosnia-Herzegovina that do. (There the word means a fresh water spring or other such source.)
The Austro-Hungarian empire had annexed Bosnia-Herzegovina in 1908, but the two component nations couldn't agree which of them should have administrative control. Instead they established a "Condominium," or shared governance, for the territory. Hence my question: during that period were Hungarian stamps valid for postage in Bosnia-Herzegovina? If not, can anyone say where in the Hungarian crown lands this stamp was cancelled?