Spent the better part of the day identifying and cataloging a lot of Bulgaria.
The last to be identified appears to have been the stamp mentioned in the note in the 2009 Scott catalog following number 157 which reads, in part, "A 50s violet was prepared but never placed in use. Value $1.75."
The catalog mentions a 1 lev dark green stamp prepared to commemorate the liberation of Macedonia that was not issued (note after Scott 127).
If anyone has a copy of that stamp I'd appreciate your posting it here.