Inverted overprints are very rare. So far, I saw less than ten such items...
1941 Međimurje, unofficial local provisional issue, 0,25 din, pair with inverted overprint. Cliche a2/3 and b2/1.
Inverted overprint overlapped with the setting of four cliches from the second printing.
For details see: 1941 MEĐIMURJE - The Clasification of Overprints.
For details see: 1941 MEĐIMURJE - The Clasification of Overprints.