I bought the following on the (I think not unreasonable) assumption that it was a Bosnian MS celebrating the deeply significant 120th anniversary of their first non-Turkish postal service.

Having got it, I then totally failed to locate it in the 1998 output of either the Sarajevo or the Mostor authorities.
So I looked at it a bit more carefully and made the following observations:
a) 200ft is not a Bosnian denomination, but it
is a Hungarian one;
b) Ferenc Svindt is a known Hungarian stamp designer.
So, no problem then. It must be Hungarian - probably a Stamp Day. And yet I can't find it listed.
Anyone know anything about it?